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Just looking at the angles of the tubes, I’d say no, they won’t fit gt40p.

But I guess you never really know until you try.
 

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No, what you're looking for is to be able to get a deep socket on the rear bolt of each tube on the driver's side. If you can it means there's room for the plugs.

I'm using MAC longtubes. They were not designed for GT40P heads but they will work. You will need 90° boots. I found the MSD Streetfire wires have a nice compact boot. I'm also using I think it's DSE boot protectors. In 2 years of use I've had zero issues with burned wires. On the MAC headers the #5 tube slips in separately after the main portion of the header is in. It is a tight fit with the plugs as far as installation. I slipped the header in, held it up with some wire, install #7&8 plugs then lowered and bolted the header in. That's the only way.

I think it's Doug Thorely that makes a nice try y that from the photo I saw looked like it would work great and better then the MAC. I can live with changing plugs on my car even though it'll be a hassle because the plugs are platinum along with electronic ignition it's going to be very long between plug changes
 

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I had ceramic coated MAC long tubes on 1995 GT with GT40Ps. Even in the cramped engine compartment of a more modern Mustang, I was able to knock out a plug change in 30 - 45 minutes. It just takes a little more patience and agame plan. I also made a couple tools a long the way to help. Best combo for me was a sparkplug socket that was cut down by 1/2 - 3/4 inch in length with the rubber plug retainer removed. With a box wrench and that socket, I was able to remove all the hard to reach plugs. I also used 90 degree boot wires on 3 or 4 of the plugs with boot heat shield sleeves.

Seems like a lot of hassle, but it really isn't. That combo made 312rwhp and 315tq with 306. Heads were ported in my case.
 

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I had ceramic coated MAC long tubes on 1995 GT with GT40Ps. Even in the cramped engine compartment of a more modern Mustang, I was able to knock out a plug change in 30 - 45 minutes. It just takes a little more patience and agame plan. I also made a couple tools a long the way to help. Best combo for me was a sparkplug socket that was cut down by 1/2 - 3/4 inch in length with the rubber plug retainer removed. With a box wrench and that socket, I was able to remove all the hard to reach plugs. I also used 90 degree boot wires on 3 or 4 of the plugs with boot heat shield sleeves.

Seems like a lot of hassle, but it really isn't. That combo made 312rwhp and 315tq with 306. Heads were ported in my case.
What cam where running?
 

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Discussion Starter #11
I really wanted something just a bit hotter than the GT cam. But I'm not really knowledgeable about cam specs. Installed a spring kit, too.
 

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Will these fit my GT40P's?
HI,

I don't know if those will fit, but these will fit : Sanderson Headers FF3GTS-SEC, I have a 67 Mustang with a AOD transmission and after going through different headers for the GT40"P" heads, I finally found some that work! These headers fit snug and have lots of room for spark plug wires.


Will these fit my GT40P's?
 

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It was custom spec'd Comp Cam that used the Extreme Energy lobe profiles. Somewhere in the neighborhood of .594 lift using 1.7 cobra roller rockers. I had to use beehive springs and titanium retainers on the GT40ps to make sure I didn't have valve float at 6300 rpm where it reached peak power. It was a great combo and idled all day long at 750rpm.
 

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68 Mustang Fastback C code, 4spd Toploader
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I have a 68 with a 289 and a 4 spd toploader. With gt40p heads, will those headers (MAC / Sanderson) allow the z-bar to also fit? In fact I have a borgeson power steering z-bar from opentracker, and I'm trying to eyeball if that will stay be okay. Those Sanderson shorties seem okay, but I wonder about the MAC long tubes. Does anyone have anything close to this working along with the gt40p heads?
 
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