driveshaft to mate 4L60 trans to older 10 bolt

[mr48chev]

That rear end should call for a 1310 spicer U joint which is pretty common in a lot of vehicles.
The front yoke would depend on which transmission you put in along with the engine and the size an spline count of the yoke for the drive shaft.

Length depends on where you set the engine in as everyone seems to do it just a bit different and even with the same engines transmissons and rear ends the driveshaft length might not be the same in two really similar trucks.

I cheat and go to my buddy's house and dig in the apple bins full of old driveshafts he has stashed out back. But if you figure out the length you need lots of wrecking yards have driveshaft piles The other option is to haul the truck to a driveshaft and have them build you a new one.