Not to be argumentative at all, but I've got several thousand miles on a .72 5th gear T5 out of a 1993 S10 in my stock engine 3600 with zero problems. The rear gears are 4.10 Eatons from a 1967 Chev C20 found in a friends classic salvage yard. Very happy with the two upgrades since I now have a very happy 60-65 mph cruiser (althought 60 mph is my normal cruise speed).
In my best info-commercial voice, the T5 is often maligned due to urban myths about it's supposed fragile nature. Many Mustang's are going 11's with a stock T5. That's not to say that strip/street abuse with slicks and 500hp (even much less sometimes) won't cause failure. Sometimes stuff breaks.
Point of information. I built a 1990 Miata with a Ford GT 5.0 (302 for the well seasoned in the crowd) that's near 300 rwhp and I've been running a T5 from a 4 cylinder Mustang for the past 5 years with no issues. It's been power shifted (old term I in know...shift without getting off the throttle, just tap clutch and shift) through 3 and sometimes 4 gears more times than I care to guess...a lot.
If you look at my little 4 cylinder unit, rated for 240 ft.lbs, no way it should still be showing up for work. I believe The thing that makes it live is my car has very little traction in situations that would stress the drive train. Wheel spin takes the load off and components last. No spin usually equals breakage. My 3600 doesn't spin, but at 85hp, it ain't gonna stress things either.
Now all the above said, I'm about to upgrade the Miata to a 2002 World Class unit that rated at 310 ftlbs primarly for the better gear ratios as in I'm currently running a .85 5th gear and will have a .68 with the upgrade.
Added in edit.... lots of info
here. To add to what Martin said in the previous post; Work a 3/4 ton or larger truck at it's GVCW rating with a T5 on a regular basis and yep, you would likely have problems. My truck still hauls 2,000 lbs of square hay with no issues, but I wouldn't spec it as it's currently set up for a freight yard or farm back in the 50's.
