transmission spline on '78 Cherokee

Hi I'm trying to rework my '78 Cherokee. It has the problem that seems to be common to this model. The spline that goes from the transmission to the sun gear in the low range is failing ( poor lube ). I've located all the parts I need except the splined output shaft of the transmission. Does anyone know of a source for this shaft? I have a 360 with Hydromatic and Bourg-Warner ( sp? ) transfercase. I have a solution to the lubrication issue but I need a new shaft. Most anything from a wrecker will be worn out already. Or if anyone knows some that can rebuild these shafts? Thanks Dwight