Any one using 3-speed with a long Bed

I need to find out what the dimensions are for either a two piece driveshaft. The front driveshaft from eye to eye, same with the rear, or a one piece. I have two seperate driveshafts with either the wrong yoke(1310 or 1350), or both pieces won't fit(too long or too short), or the carrier bearing doesnt alighn on driveshaft with crossmember. I can get a used one pretty cheap, with no dents or misused, but I need dimensions. I took out my 4 speed sm420 out of my 72, and put in a three speed from my 68. I don't want to buy a new one b/c I'm gonna get a new one when I put in my 700r4. Any help would be NICE!!!!!!!!!!