It depends on several things. The 7.5 lives fine in F-bodies behind some respectable torque, but they are very traction limited. The tires go up in smoke long before enough torque gets put to the 7.5.
If you put more than about 350 lb-ft to it and you get any shred of traction, there is a very good chance you'll rip the axle in to pieces. Small bearings, small ring gear, and a small casting. It was designed as a lightweight economy axle. It takes some abuse, but not where traction is involved.
If you feel saucy, go for the 8.5 from a Grand National or 442. They're not as hard to find as you might think, and if you get one from a flat-rate junkyard they're no more expensive than a Chevette axle.
The flat-eared axle you have is probably an 8.2. Its a little better than the 7.5, but if you're putting a 144 blower on things I'd go at least 8.5.