GT40 / GT40P

Thanks for the input everyone. I have been following the "Custom 1965 Correct Craft Mustang Build" thread and enjoy it, but I am not looking to build a restomod. I am only considering this engine work because I have a spare H/M engine that's locked up and it would be nice to have a fresh engine. I work slowly and I don't want to make more work for myself. I also want it to look all original, at least with the motor cover down, and I NEED it ready before Green Lake next summer. The engine work requires nothing from me other than dropping it off at my engine shop and picking it up fresh and detailed. The original engine runs good and I can set it aside complete with all the correct pieces. I suspect my spare tranz is probably just a core and that they are not worth much if anything in that condition. I plan on re-using the original. There is plenty to do without making more work for myself.
This boat will be used by my wife and kids and I don't want it to be more than they can handle. I sold my last boat for exactly that reason If this Mustang is capable of a deep water barefoot start (not for me) and looks good with a few old cotton tops in it, it is good enough for us. I don't intend to show it, Gary has that base covered.

I do.

The '69.5+ flat top boxes fit over 351's as the same box was used on most boats (ski nautiques included) through '82. The curvier boxes used prior to that will not fit a 351 underneath unless the manifolds are very conservative and even then questionable. Wood boxes came over the wider chryslers and even 302 HM's.

Most people who know engines half way decent would spot a 351w in place of a 302, the width is pretty easy to spot. With the power levels being discussed here, no reason to step up to the larger block. For a 400+ hp build, I'd think differently.