MA5 5-speed to 5.7 hemi?

Couple of thoughts.

In regards to the gear ratios, The newer Mustang GT's with the 6 speeds (MT82, not the T-56 derivatives) run a 3.66 first gear, and a 3.55 final drive. That gives a 12.993 SLR, for comparison. The ratio spreads are better on that trans, though, as the GT get's a 1:1 fifth, so more spaces to spread the drop over. On the MA5, the splits are about 40%/40%/27%/27%. For reference, the standard A833OD has a 45%/40%/27% spread. So, in theory, a 1-2 shift and 2-3 shift on the MA would feel like a 2-3 shift on an A833OD. And the TKO-500 and R154 both have about a 40% drop from 1-2, too.

In regards to the flywheel, I know of one person that has relocated the pocket on the 3.9 bellhousing to work with a 130T flywheel. That is my plan for my R154 swap (if I ever get to it), and I got started on the layout for a jig, but haven't finished anything. I was working on building a plate based on a 727 bellhousing that would use the motor to bell holes to locate the starter pocket holes correctly. Then I was going to cut the pocket out, use the plate to locate it, and get it welded back together. Just an idea, but it would make it easier to find a flywheel. And it would solve some issues with the starter you will have to deal with since it is farther out into an area that is already way too tight.

Lastly, I would talk to Spec or someone about a clutch. They did a custom clutch for me when I was going to run my R154 behind a turbo slant. Built me a Stage 3 clutch that was the right diameter and splines to match up. Don't remember the price (it was a group buy on Slantsix.org), but seemed reasonable. Too bad it was a complete waste of money as the car and the project is long gone. Either way, they should be able to build you a 10.5" or 10.95" clutch to fit a standard 5.7 swap flywheel, and put the right splines in it, and I doubt you will need a Stage 3 to make it work, either.