staying with your thought process---I do have to say that restarts are huge in the crate game
the torque of the 602 already matches the 604 at restart RPM and couple that with a 2 speed trans you should be able to make a spot or 2 on starts---if the driver can get in the prefered groove quickly after the start then maybe you have something.
here is a suggestion ---use a 750 carburetor to enable the engine to breathe a little longer
we have not used anything other than 650's for several years to keep the restart strong but in your case with the tranny ---the start should have plenty of giddy-up but you are gonna lay down early----a 750 carb will help that
I might even try a big header---both of those are the opposite of what we do but we do not sell to guys with 2 speeds so there is more to be considered
just thinking out loud---might not work at all but you are already outside the box so I was staying with it
Brad
www.race-1.com