From the 2004 FRPP catalog:

"Extensive dynamometer and in vehicle testing has confirmed that this block should not be used for engines exceeding 450 HP @ 6000 RPM." (this is PN M-6010-B50)

PN M-6010-A50 (the Street Production Replacement) is rated at 400 HP.

PN M-6010-R302/M-6010-S302 (Professional Competition) are rated for 1200 HP @ 8500 RPM

Specs for the Aluminum Race block are not listed.