O.K. we performed the swap and we got the car running but for some reason that me and my buddies dont know the car boogs down when it is in low rpm and once you get it in the higher rpm range it runs just fine what could be causing this and it is not throwing up a cel? Any kind of response would be very helpful.
Thank You

 

Sounds like the timing is retarded. T-belt off a tooth or distributor pulled back?