upgrading a 300HP mag motor for a street car, I think I'd use a cam like a hughes 1828, not something as big duration wise as the 380 horse motor. Zippy, I thought the 300HP motors got the upgraded springs, too.

the dual plane isn't a bad piece, it's on par with a stock LA 4bbl intake. an edelbrock air gap would probably be worth an additional 15-20 HP...

the M1 single plane is a good intake, probably makes about the same or a touch more HP as the air gap, but like most single planes, is probably down 15-20 lb ft of midrange torque over the air gap or the dual plane....