Help with dead pony

[nitrostang66]

Well not quite dead I hope....I had an accident with my 66 last year and after 7000.00 in paint and body work, not to even think about insurance problems(they think because it was 37 years old then it must be a peice)it is back in my garage. The problem is it runs like crap. My baby has a 302, 351 heads and msd, along with the reg. mods. The engine was put in right before the crunch and all parts are new or 2 years old. Lets see if any of ya'll have run into the problem I have before.
Duel exh. with headers. makes a very puttering tone, small backfires in idle, on the street a loud one every now and again.
When you rev the engine in park on the backstroke of the gas you can hear a metalic fluttering that is very low(like a groan in a metal chair when you lean back)
The car will not stay on after you start it, unless you hold the gas a bit down for a while. and if it is started will now and again shake noticably.
There is no leaks on any part of the car(oil, gas, trans, rad)
If I am stopped and hit the gas the car will bogg down, and is hard to get up to speed.
I have to move it soon and would like to fix it before I do so so any help would be great.