driveshaft problems.....please help

[owa1000]

So i picked up a 67 gmc swb and now im trying to get it on the road i have run into some problems. Im trying to hook the drive shaft up but cant seem to find the right u joint. The u joint that came on the drive shaft seems to be to small for the pinion yoke on the rear end. I dont know if this helps but I have a 400 trans and it seems to be a 8.5 10bolt. I have tried several u joints and either they are to big or to small. Does anyone know what i could do to get these things to line up. Im new at this and any help would be appreciated. thanks everyone

here is a quick pic