Is a 7.25 rear strong enough?

I only have experience with one open 7.25 behind a 380ft lb motor in a 3500lb Duster. It held up to me bashing on it once in a while. I was gathering parts to build a shortened Ford 9 inch.
I've a second 7.25 under a87' 5th Avenue that I'm putting together a 290-300ft lb 318 for a weekly driven town car. If any more torque than that I wouldn't roll the dice and would swap in an 8.25 or bigger from all of the horror stories I've heard about the 7.25 from the old timers.
Just for Future reference, building that shortened 9 inch cost @ $3000 in 2018 dollars with a free housing that my Brother found at work.
It seems that the days of going to the junk yard and finding a 8.75,9 inch or 12 bolt for $50-$100 are gone. At least ,where I live they are.