New 360 what time ?????

Headers.

Certainly the camshaft is the problem but should I be going backwards this far?

Anything is possible. Did you degree the cam when you put it in? If you don't want to pull it outright, check the lash, check the lifters, etc.

Since it's a new shortblock, I'd do a leakdown before anything else. Make sure you're not having ring seal problems (or you don't have a bent valve or something).

Steve