I beat on my 5R55 pretty hard over the years and it's holding up so far after 5 years and 68,000 miles.
First on the car was 100 shot Nitrous with bolt-ons, ran like that for 1 1/2 years and about 25-30 track passes with a few street runs.
Next, Saleen supercharger, started out with 3.4 pulley and dropped down to 3.2 pulley, ran like that for 3 years, with alot more track and street runs.
Now 302 stroker 2.8 pulley and more track runs, been running this setup for the last 6 months and everything seems to be going good so far.
having new dynotune done next week, should be in the 565-575RWHP range.
All that's been done to the 5R55 is= swapped out servos for the billet servos and swapped out input shaft for billet input shaft.
Stock for now.