Engine Performance problem
1974 Dodge Coronet V8 Two Wheel Drive Automatic 200000 miles

Hi friends. I have a problem unique : it appeared suddenly . Last night , when i started my car , it was OK, but when i connected REVERSE , the engine started to fail and quickly turned OFF. The same happens when i connect DRIVE , but the case is worst when i connect REVERSE and try to accelerate ( the engine turns OFF ) . The engine has a NEW 4 barrel thermoquad , the engine is a 318 in good shape. The tranny is a Torqueflyte 8 .
In NEUTRAL the engine runs OK, but when i connect REVERSE or DRIVE , the engine dies.
What can cause this failure ? A friend mentioned me a vaccuum leakage as a probably cause of this malfunction. I ´m noy sure .
Thanks in advance

Richard.