8 3/4 A body axles 28 3/16 long

I have a clutch type center section in a A body 8 3/4 rear. I installed 28" long axles, started the car, and it wont move. Mancini Racing tells me I need, A body 28 3/16 long axles. I can't find these anywhere. I also want to stay with the small 4" bolt pattern. So if any of you guys can help me, I would appreciate it very much. Mancini has them new for $480, but Im old and have limited funds. Thanks Jerry