Purple Shaft or NOT?

IIRC

The XE comp line is ground using the Ford lifter ramp rates, the HL series is ground using the more aggressive .904 lifter ramps.

That 284/484 will be pretty tame in a 400+ inch engine. They sound and run real good in 340/360, but a 408 will eat up that duration. My general feel, if you know how something runs in a 360, add 12-15* to it at .050 and it will run about the same in a 408. I'd look for something like Moper suggest, the voodoos and Comp XE- HL series cams work really well.

410 with a Comp XE295hl
http://img192.imageshack.us/my.php?image=irwindalevids002.mp4
http://img13.imageshack.us/my.php?image=irwindalevids003.mp4