Jasper crate engines?

I've heard good things about Jasper motors, and am considering one for
next year. I think the Paxton blower is probably not the best way to
go.... well... maybe later on

Has anyone bought one of these? Do you know if the advertised HP and TQ
are accurate? I always heard that a rule of thumb was you had to spin a
302 to 6000 or so to get 300hp out of it. Their Stage II 302 is
advertised at 300 @ 5500 rpm and 321 lbs./ft. @ 3700, "SAE standards".
I don't know if this is the same as SAE Net. (??)

This is a desirable option for me cost-wise because I wouldn't have to
replace the carb, manifold or any accessories, and wouldn't risk blowing
the 8" Currie I run. And if the power numbers are accurate, I would
likely get the mid 13s I want with my Tremec and 3.80s (assuming good
traction) and retain drivability.

The far less costly option is to do a cam and head swap on my
parts-store ATK motor, but I think the increased frictional losses would
prevent me from making the power I want to (300-325). Plus I don't want
to spin the hell out of a mediocre-quality engine, or supercharge it,
then blow it. I'm not any sort of expert with building engines
(obviously) so I don't know if my assessments are accurate or not.

Any suggestions, comments or other ideas would be sincerely appreciated.

Thanks,

--
Wound Up

1967 Mustang coupe, restored & modified

Remove "put her" to reply in that bucket