Snowman51
Assuming you are working on a 3100 series, AD truck (short bed) and, assuming that in my 1957 3100 w/SM420 has a comparable length driveshaft, I offer the following:
my (org) driveshaft is in the neighborhood of 60"+ long. Single shaft with slip just rear of the transmission. Served me well for ~200,000 mi in 60's, 70's and 80's. I will be reinstalling it when current and long going resto is complete. Trans, shaft and rear end are as from factory.
delky dave in wyo