IZ28

Because if you plan on lightly modding or even some heavier mods 3.73's can be too much for a TPI car especially at high RPM's. Wanna shift into 4th at the end of the 1/4??

demonspeed

4th isn't a big deal to me. I'll definitly be hitting 4th with the 3.55's in my mustang, so that doesn't make a difference to me. I mean, 3.73's would be difficult due to the low end torque, but they snuff out up top... but I mean, it's a heavy car too.

IZ28

I think the highest I'd go with TPI is 3.45's. Gears from 3.27-3.45 match the way the setup makes power the best. I've heard of people putting in 3.70-3.73 gears and not liking it. They liked the launches, but that was it. They also didn't like to drive with on the highway too.

demonspeed

That's where the double overdrive of a 5th and 6th gear come in. It's not like 4.10's or anything...