I'd rather stick with the 3.69. 1st gear is already useless as it is, I wouldn't want 2nd any shorter personally. 3rd and 4th are a blast :-D Also, RPM is not the main factor in spooling the turbos for "usable" power, load is. I'm not saying that I am 100%sure the 3.69 rearend is better than the 4.10, but that's my theory. The only changes I would make with gearing, would be in the tranny. I'd make 1st and 2nd longer.