How strong are 8 1/4s

If you still have you 7 1/4 in it, do a massive burnout with can count how many seconds it last doing it. Mine last 15-16 before it stopped working.
:-D I have to tell you my "back in the day" story about my first 7 1/4 blow up.

I am 17, in 67 and took my "almost new" 64 Barracuda, 273-2 4 speed to a drag strip, 75 miles away, in Ark City, Kansas.

Well, it turned real ugly, real quick. I was broke, and broke down, it busted the case.
Got a couple friends to come after me with a tow rope, and it would only tow, after I took the carrier out of the rear end. They were no longer friends after that, as it was one crazy ride. The axles were flopping around inside the housing.
It was one heck of a mess, as I had just moved out of my parents house.

I ended up finding a brand spanking new wrecked 67, in the salvage yard, and changed it over to the 8 3/4. It was $100 at the time, and that was big money. Not sure where I scraped it up.

Now I have probably converted over another half dozen since.