Thanks, Mickey2! You have been very helpful as I hadn't thought of the timing. One was made in 1949 and the other in 1951. Guess I will decide if I actually take the 15K88. The motor that was on it doesn't appear to be a potted motor like my 15-91. It is more square in appearance at least on the pictures that were sent to me. Will get more info. Thanks for all your input.