284/484 mopar cam for 340

Like was said - your compression is iffy unless the receipts you have say it was blueprinted to that (meaning it was measured - and you should have the measurements on record somewhere...). If you have less, the cam may be a little doggy below 2500. You should degree it regardless, but you should also listen to Cracked and install it advanced a little. It will help with the idle and low end issues.
Personally - I'd stick in the XE268 with 901-16 springs and call it done.