Here are some serial no. auto/engine combinations: proto Avanti - 10001, R1236 - 10445, JT1831? - 12372, R5642 - 14561. This would suggest that approx. 4560 units were installed in factory cars. The JT1831 & 12372 combination is not certain, but very probable. The time sequence would be about right. I'm sure the American Motors "powershifts" carrying the "A" suffix would have their own serial numbering system.