What year 360?

1971-1974 uses the 3418496 block, but a few slipped out in '75.

I wouldn't complain at the build you already have, @ 445 RWHP is very respectable for a 360 with a lot of stock parts still involved.

A grenade won't blow if you don't remove the pin, so if the engine quits pulling at 5500 rpms, limit it at that, or a couple hundred under, and it'll be with you for a while.
I think you have already found something that works really well, IIABDFI, in my opinion.

Mark.