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Hi. I have a 68 coupe that I purchased to restore with my girlfriend's dad(he rebuilt old dodges(a '73charger and '75 valiant) with her older brothers and he's not the most knowledgeable about fords and I wanted to know if ya'll could answer some of my questions.
1.) It's a 3-speed manual with an inline 6 and I was wondering if I was to upgrade what engines and transmissions would be a good fit(I found a 289 and a 4 speed for $750 and wanted to know if that was a good deal.
2.) If I didn't change transmissions and kept the 3-speed would it handle a bigger engine or would it have issues?
3.) Would the straight 6 work better if I put a 4-speed in?
4.)Or should I just get both the V-8 and a 4-speed?

Sorry for the long post. But any knowledge or help would be greatly appreciated!

Thank you.
 

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The options are limitless. There are a few things that you'll want to consider, of course.

a. The 6-cylinder cars had smaller brakes and 4-lug hubs. That can be an issue when converting to a more powerful and heavier drivetrain. The 4-lug wheels limit aftermarket wheel choices somewhat.

b. The 6-cylinder cars used the very weak 7-1/4 inch integral-carrier rear axle. There are very few choices in different gear sets for these.

c. The 3-speed transmission used behind the 6-cylinder in '68 and later is the heavier duty "3.03" unit that is essentially a Top Loader 4-speed with only 3 forward gears. It's plenty strong to sit behind just about anything Ford stuck in a '68 Mustang, including the 390.

Besides the brake and axle considerations there are some other differences between 6-cylinder and V-8 cars including springs, fuel lines, throttle and clutch linkages, engine compartment wiring harnesses, radiator and hoses, and probably a couple I've forgotten to mention. What I would suggest is to keep the existing drivetrain and get the car in good basic mechanical condition and THEN proceed to the interior/exterior. After driving it some if you think you'd like to consider a different transmission the best choice would be a T5 overdrive 5-speed unit. There are a number of modifications that can be made to the 200 I-6 including dual exhaust, electronic ignition, throttle-body fuel injection, supercharging/turbocharging, etc., and the basic engine is quite durable, having 7 main bearings.
 

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If you decide to go with a V8 any 289, 302, 351W, 351C, 390 or 428 will bolt right in. I believe your 3 speed is what is known as a "3.03" and it is a Toploader design just like the 4 speed Toploader so it will handle any of the V8 engines except the 390 and 428. However, your 4 lug front and rear spindles/axles will need to swapped out for the 5 lug version.
We can't make your decision for you it's entirely up to you. If you want to drive now stick with the 6 cyl and 3 speed.
 
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