Yeah, that what I would say. I would let a few more people chime in who actually have Mustangs, but with 4.10s and the stock engine and the stock first gear in the transmission, im sure that it goes through first pretty fast. The thing is, you want the engine to wind up fast to get it into its torque range if you have a higher end engine, but with the supercharger your going to flatten that torque curve out and raise it all through the rpm range. With the extra torque, you would go through first like nothing and will do a few things that, in my opinion, will actually make your car slower. First, going through first so fast that its not going to be in the max torque range very long and will not pull its hardest for a long time. The gear ratio multiplies torque by the given ratio, but having 4.10s would leave you (not just in first but the effects would be more noticable in the 5.0s short first gear) making your max torque for only so long. With 3.73s, you might not make as much torque peak, but over the whole gear, if you averaged it out for the amount of time you spend in that gear, you would probably make a very similar amount of torque for a longer time. The 5.0s also arent a very high end mill either, around 5500 rpms is where you want to shift, sometimes lower. Anyway, here you can take a bit of advise from some Buick, Olds, and Pontiac 455 bruiser guys. They will often use tall gears, like 3.55s, because those 455s cant rev high, they usually need to be shifted around where 5.0s do when they have a strong bottom end to handle it (remember, they have very long strokes which arent stable to rev very high), but the things pull like a damn freight train from right off idle to where they need to be shifted. If they used 4.10s, sure, they would be putting more torque to the road, but they would also be shifting very often and their engines would be running out of breath near the end of the quarter. I hope im making sense to you lol, sometimes im pretty good at making things sound more confusing than they are.
I like to let 'em stick with me for first and second, then I put the hurt on 'em when I chirp third ~
1967 Plymouth GTX, work in progress.
440 cubes (thats 7.2 litres for you modern guys)
480 ft lbs of torque
MODS: Direct Connection Purple Shaft cam