[fastd]

if you go to a tko600 (with a 2.87 first gear), I'd leave your 3.31 gears alone. If you keep your toploader, i'd might keep the 3.31 gears also, i.e. your first gear is kind of a 2nd gear; I'd rather have that than having a 4rth gear that revs you so high at 60-70 mph.

Given power and weight, I think the optimal first gear final drive, i.e. 1st gear ratio x rear gear ratio, to be in the 8.0-9.0 area - that way you get a nice pull in first, not just 20-25 mph and then have to shift. I like to be able to get up to 50 mph in first at about 5000-5500 rpms.