I have a 83 T/a with a 700r4 and a stock 10 bolt. I have an extra 700r4 out of a 86 berlinetta (Still need to see if its the better style of the 700r4 from 87 model year) I have a 400 sbc short block right now and am finishing the top half soon hopefully, if im lucky pushing 450 hp. The main issue I have is with the strength of the rear and trannies. I know that punching it at a stop light wont help their life, but would it be safe to get down on it when on the highway? At speed already I would assume less force on the rear and tranny. It will probably be atleast a year before the rear and tranny are replaced. I dont want to break them but it sure is hard to hold back when the 85 rustang with his stock 180 hp 5.0 blows by at 90. Will it be able to handle full or mostly full throttle at cruising/high way speeds?

 

450 HP will blow up the rear end pretty easily. I blew up a 9bolt putting about 325 to the ground.
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Id worry more about the torque.

 

Your 9-bolt was already going out. Many people have put much more than that to them, no issues. I'm running 11's with a 1.6X 60ft on a 10-bolt, but it's far from stock. - As for a stock 700r with unknown mileage/abuse. It's hard telling what it'll take.

- yes, a rolling punch is usually easier on driveline than launching.