Almost to the point of purchasing a 1968 AMC that had the 390 and Borg Warner four speed - but sometime during it's life had an unknown AMC 360 swapped in. Will my 74-78 AMC block bolt to the original four speed without to many problems? I'm having the AMC 401 balanced with the flywheel. I'm sure the two will bolt together but is there something differnet with the crankshafts?