550-600 hp I wouldn't bother w/ a girdle. twocents
I had a .030" over 440 that made around 625 hp w/ just ARP main bolts and stock caps and it was fine. Caps were walking of course, but no problems. Put a lot of runs on that motor.
That motor later got freshened up w/ some upgrades that put it at the 700 hp level, but I ended up selling it before I ever put it down the track.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 4 speed, Dana 60
'71 Demon 340, no drivetrain, on blocks behind the barn
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax