First I would swap the IRS for a live axle. Then get 4.10's or better, I know you said you wanted 3.73's.
I have:
live axle w/ 4.10's
O/R H pipe, Dynomax ultraflows, eibach springs, timing adjuster at 16 degrees, Steeda pullies, only using crank and waterpump, Pro M 80mm MAF w/ K&N...