I've got a '73 Power Wagon 3/4 with a 360 that I can't seem to get to run right. Below 1500 rpm is not so rough but when you push on the throttle it acts like its flooding out and even backfires occassionally, it's really bad when the engines not hot. Above 1500 rpm it runs like a dream.I'm not good with carbs so thats probably where the problemis (its a Holly 2 BBL). I've timed the engine and replaced all the basics. Any advise on where to start?

 

Sounds like A excellarator pump problem - clogged, ball not seating, wrong excellarator pump cam.
I have had the same problemn a 4-Barrel, wrong cam on pump.

 

Make sure the vac advance is workin' and hooked to the correct port also. No vac. till you open the throttle.

 

Also sounds like a loose timing chain. Check your timing, and see if it changes drastically above 1500 rpm, or if it seems to bounce around. My father in law had the exact same symptoms on his 360 PW. Chain was loose, and actually rubbing the timing cover.