I have a pair of the 525SC's in a 38 Donzi zx with about 225 hours on them with no problems at all. They have always run perfect and i run them pretty hard. Toss on a pulley and intercooler and i have been told 600+ is not a problem.
I also have 454 mags in my Scarab that run great as well. these with about 550 hours and still run'in strong. either motor should fit your application but i think i like the SC's better.