help identify this transmission. Supposed to be A518

The 518 was used for a few years before the magnum came out. It sounds like the one you have came from behind a TBI 360LA. I have read that some are not lock up, but I have never seen one. Yank the converter out and look at the input shaft too see if it is a lock up. If the shaft stops at the splines like an old 727 its not, if a machined snout extends past the splines and there is a hole in the center its a lock up. The non lock up trans would only need a 2 wire hook up. The balance on that converter is different than a magnum motor.