I thought this was going to be what do you prefer, then I was bummed there was no 3.73 option. I tow heavy with my early zf and 3.55s and it sucks. First is too tall and so is 5th. I have towed heavy with 4.10s, 1st is about right and 5th is too low. I think a late model zf with 3.73s would be the perfect setup. Tall enough first to get going, but enough grunt to stay in 5th most of the time, with 4th there when you need it.