yoke size?

So im getting a driveshaft made to fit my car and i tried sticking the driveshaft in to measure it. wouldnt fit, the old duster yoke is too small for the tailshaft. I believe the trans came out of a mid 80s truck. What yoke will i need to fit it? and i would imagine it would be best just to stick 2 new u joints on the driveshaft as well? whats best?