First off, thank you all for your time and information. its greatly appreciated as this is getting frustrating.
What I (think I) know about the truck:
I purchased the truck last December from a guy who had bought it 8 mo earlier. He bought the truck as is so doesn't know exactly what the configuration is.
Truck appears to be a 71 cab and frame with 67 clip and bed.
SPID, which I believe is original, shows 71 long bed (127) w/ 350/350 combo and 1G50AC Heavy Rear Spring
Truck currently is a short bed, 400/350 combo. Welds are visible just behind the support where the shaft bearing mounts. The cross support appears to have holes where trailing arms would mount along with the bearing mount that is specified for trailing arm suspension. Truck has leaf spring suspension on it currently. I don't know what this truck had originally, why it has coil spring cross member and bearing mount but leaf springs. The back half of the frame may not even be c10. The only "slip joint" my driveshaft has is at the transmission.
In looking at this picture I remembered that just before the original mount broke it was bent towards the drivers side of the cross member opening.
