Well a vacuum leak will keep a engine from idling. I agree you need to check timing at idle. That big-ole cam would like lots of initial timing...Probably 20+ deg would be best.
Recheck the timing, and for vacuum leaks and report your findings. Use some Brake Klean, or carb and choke cleaner and spray around the intake mating surfaces and carb base gaskets etc.
But you say "it Wont idle in gear"
Makes me think it will idle in Park?
Stupid questions but how loose is the converter, and large cam like that and a stock converter WONT idle in gear.