I recently purchased what I believed to be a 743B but I am beginning to wonder. The serial number says it was built in May 1991 but the unit has the old style one piece axle and manual fuel shut off. Did the early production 743B's still have this configuration? From what I've read, the 743B's were built between 1991 - 1993. I also thought they changed from a vane pump to a gear pump in the B's. Anyone got some insight on this issue..