My take on things is that cylinder heads are not super chargers and not turbos. They’re only going to improve performance if your current heads are a restriction to your power goals. Being automatic especially you need to be more particular in matching everything. The 289 is a great little engine but it’s big problem is being a short stroke and large bore means your combustion chambers are going to be on the large size and volume. Keeping that ratio in size to the volume of the cylinder is going to be more challenging. When Ford advertised the compression ratios of theses engines are more “advertised”. Very simple calculations excluding a lot of important factors such as valve reliefs, head gasket volumes and exactly how far down the bore the piston is at TDC. These are mass produced and not blue printed engines. So it comes down to instead of a A code 289 having 10:1 it’s closer to low 9’s. A C code is what 9.2 or 9.4? It’s probably much closer to low 8’s. Now a lot of aftermarket aluminum heads are more geared to a 9:1 compression on a larger 302/5.0 engine and as such have around a 65cc combustion chamber. As I said a C code is probably closer to low 8’s and that’s with a smaller 55cc chamber or so Ford says. That extra 10cc of volume is a easy full point loss in compression.
Now aftermarket heads are going to breath much better and are going to fill the chambers much better which will offset a lot of that compression loss. Except at lower rpm where the engine will feel lazier. I would lean towards having a shop go through your current heads. Put the larger 351W intake and exhaust, they’re 1.84” for intake and 1.54” on exhaust. A mostest increase but then again you’re doing modest work. Your shop will do a multi angle valve job, clean up the valve bowls, nothing crazy and slightly open the exhaust. It’s not crazy work and not going to be crazy expensive and should give a very nice bump in performance. For a cam, nothing crazy. Something like a RV type. But don’t ask me for a specific cam, who knows I could recommend a Cummins diesel cam. Call a cam company. They will ask a lot of questions and give you free expert advice.
For intake, again nothing crazy. For your use and build a Edelbrock Performer 289 will or should be fine. They are designed to work on street cars in rpm range where we drive most of the time. You should be able to find a good used one reasonably, about $125. For exhaust shorty headers will be fine. A stock 2” dual system with a turbo type muffler will be fine. A few years ago I put a junkyard Explorer GT40P into my 66. Initially I was going to run stock exhaust manifolds so I could do a 1 day turn around on swapping motors and put headers in during the winter. I was really eager to see how my exhaust manifolds would work. I hade matched the manifolds to the exhaust ports which are much larger then the 289. I also noticed the outlet of the manifolds severely reduced in size just before the exit. I would say maybe 1.5”! I ground them open to the full size. Unfortunately never got to use them as the Z bar adapter for the clutch linkage prevented that.
I would highly recommend sending the distributor out to a shop that does recurring. This is a great low hanging fruit modification. Probably one of the best things you can do. It really can make or break your engine performance. I can’t say this enough!
You don’t need to go crazy on mods just have everything working together. As I mentioned I have a Explorer 5.0. Nothing crazy, only thing I did was swap the cam for a stock Mustang 5.0 cam that is slightly hotter. It’s all cheap used stuff. I have maybe $1k into the motor and that includes the motor, new billet flywheel, new balancer. I’m having issues uploading a clip to YouTube or I’d show you how well a somewhat sorted out combination of parts will work. I’d suggest thinking of swapping in one of these motors but you said you want to leave the motor in which is ok.
As far as suspension. I don’t race but I did do a lot of work on my suspension. All aftermarket tubular control arm. I spent a lot of time understanding what I needed to do. I’m happy with my results but what’s right for me is not for someone else. I’m not trying to talk you into what I did but more to say I went down the same road as you are now figuratively speaking so I can give you some hind sight thoughts. First you absolutely do not need to do what I did to have a great handling car. The absolute most important thing is to have everything in good shape, no worn out stuff. The single best thing you can do is lower the upper control arms period. I like the roller bearing idler arms. Bart raised concern about roller bearings for a static load. He’s pretty much right. You typically do not use roller bearings for static loads for his stated reasons. I avoid using them for a while for these reasons. I’ve been to a roller bearing seminar too. It wasn’t until I saw roller bearings listed for static loads did I give it a shot. 10 years later, no issues. Besides if nothing else they’re going to far out last stock rubber bushing perches and who wants to change them on a regular basis? If the money is there, adjustable struts. You can fine tune caster but the money shot is that they act consistently where as the stock set up with rubber bushings that compress erratically don’t. They’ll improve day to day driving but they’ll really shine under harder braking. The car will no longer dart around but will simply stop dead straight. Nuff said. Shocks, you get what you pay for. Good handling does not mean stiff ride IMO. If you can I highly recommend investing in good shocks. Either Koni or Bilsteins. It’s money well spent. Last, good alignment. I would say 1/2* negative camber with as much caster as you can get. You want at least 2* positive caster, 3 would be great. With the stock suspension with shims you’re going to be limited and it’s going to come down to a dance between caster and camber. Do anything you can to stiffen the front end up. Such as a Monte Carlo bar between the shock towers and a export brace between the towers and fire wall. Install a 1” front sway bar. You don’t want or need one on the rear axle with the leaf springs.
You don’t need to spend crazy money just buy a few right parts. Don’t be in a rush to do this or that because you’ll probably end up redoing it later arm. The more you can learn, the better off you are. Have fun driving it in the mean time. This photo was from a opening day at Watkins Glenn. 3 paced laps at 55 mph for $25. They’re typically fun and a couple times they got a little lax with speed and I saw 115 mph a few times on long straight sections.
