So you will be ready to head up to Peasanton in June, right?
My two cents. If you have the choice, pick up the 2.66 first and .63 overdrive version. I picked up a t56 magnum a couple of days ago for a number of reasons and I'm looking forward to the different 6th gear. Even with an LS engine, the .50 6th gear sucked. 5th revs on the high side for freeway driving, so I usually leave my car in 6th, but it is pretty useless under 75 mph. I don't even hit 2000 rpm until I'm going over 80, and I have 3.73 gears. I can only imagine what it would be like with your tall tire out back. 3.90 or 4.10s might work better but you'd probably be shifting out of first as soon as you got rolling.
Matt