n2oracer

I'm hoping to finish my 84 Regal soon. I'd like to hear some opinions on which transmission to use. The car will be a toy I take to the track about once per month. I might even try my hand at bracket racing. I want to go as fast as possible, but be reliable. The choices will be a Turbo 400 or a Powerglide w/ stk 1.76 planetaries. The trans will be built with good cluthes and a transbrake. I have a BTE 8" C100+ converter that will be used, should stall around 5500 RPM.

I'll list as much info on the car and engine as I can. If you need more, I'll try to answer.

CAR
84 Buick Regal
approx 3400 lbs
bolt-on stock suspension
double adj upper/lower control arms
anti-roll bar
29.5 x 10.5 slicks on 10" wheels
9" w/ 4.30 gear

ENGINE
BB Chevy 4.375 x 4.000 481"
12.25:1 CR
6.135 rods
990 heads with 2.25/1.88 11/32" valves
bowls blended, short side radius reworked, and chamber unshrouded
flow numbers are for #6 port(bad port?) & no pipe on exhaust
.100 72/59
.200 143/113
.300 215/139
.400 261/165
.500 290/186
.600 306/204
.700 323/213
.800 333/216
Howards solid roller 7/4 swap
ADV 314/322
050 278/287
200 187/196
110 LSA/108 int CL
lobe lift .439/.430
valve lift .790/.731
rockers 1.8/1.7
Weiand 4150 Team G with 2" 4500 adapter
opened up (still has some venturi) and blended on intake side
#9375 1050cfm Dominator (stock non-HP style)
intake has no port work to plenum or runners
Hooker super comp headers for G-body
2" x 30" primary
3 1/2" x 10" collector
3 1/2" Bullet mufflers

It should make about 650-700 HP. Shifts will be around 70-7200 RPM. What trans should I use? Any thoughts on what the car might run?