Did you truck originally come with a two piece driveshaft?
I have a '50 3600 with the two piece driveshaft and I had it converted to a single driveshaft when I installed a T5 tanny- it was no problem. 4" diameter tube. I don't think your driveshaft length would be any longer than mine...
But, I installed an updated rear axle and so I measured driveline angles and welded new spring perches... it is entirely possible that converting to a one piece driveshaft without changing the rear axle would require shims at the stock perches to get the driveline angle where it needs to be, since that angle will change with a one piece drive shaft.
