I have a chance to buy some GT40 heads from a 93 Lightning. Will they fit? Will I see gains? I think I will have to use "special bolts" that are stepped from 1/2 to 7/16. Does anyone know what cc's my stock heads are and the 351 GT40's ? I think I can buy them for $300 complete. The truck they are coming off of is running 14.80's now. I have put a Lightning rear in lately (4.10 Trac-Loc) and underdrive pullies. My 93 ex-cab 2wd runs good now, but I want more. It is a Speed Density 5.0 with E4OD. Any input?

 

GT-40 heads are a good upgrade for the 302. They have approximately the same 65cc chambers as stock heads but flow much better due to the bigger valves and better ports. They are also smog-legal in all 50 states. Use Ford head bolt kit M-6065-B289 to install them and you'll have no problems there.

You may run into some problems with the speed/density PCM, it's much less forgiving of mods than the MAF. With no other mods, it's likely you'll squeak thru since the S/D system can tolerate values up to about 15% outside of expected parameters. You can always convert to MAF by getting the correct parts from a boneyard 95 if you need to.