I have a 1969 /6 dart . just put in a rebuilt 1978 supper six engine and 904 tranny with a B&M shift kit installed in it. The engine runs great starts right up idles smooth The problem im having is when put into drive or reverse the engine stalls.even if i keep my foot on the gas it will still stall. I adjusted liffters checked vacuum 20 psi timming set at 12*checked air fuel mixture checked for voltage drop (msd 6 a magnetic pick up distributor) EGR has been blanked off.I dont know what it could be I drove this car (1978 aspen) around before I pulled the motor and tranny and it was fine . Any help would be much appreciated