I agree with RK on this one, i think the 700R4 will be toast after a short time and you'll have spent $2500.00 to have it built.
Jim Hughes build a pretty serious 4L80 trans that will probably stand up to 900 HP, but they are not cheap.
Another alternative is to build a good PG and put ( Gear Venders OD ) on the back of it, they are good to 2,000 HP, and almost all the street cars that run the worlds fastest street cars use them.
I too have been drag racing since 1956, and have run everything from stock to blown alcohol big and sm/blk engines
JMO
Zip.