drive shaft shortening question

[johnw893]

I swapped a dana 60 into the rear of my 69 k10 this weekend and after putting the drive shaft in it is almost completely bottomed out in the slip yoke even after I moved the axle a 1 1/2" back to correct for shackle flip. I know it needs to be shortened cuz when I test drove it I could feel the gas pedal moving when I went over some bumps. So heres my question my truck has the 2 piece drive shaft so I was woundering if I can just cut an inch or 1 1/2" off the male splines of the first shaft I figure it's the same as shortening the rear one but easier. Would this work or would I still need to have it rebalanced it's not a speed machine it will only go 70 tops. Also any tips for changing out the center support bearing mine is pretty shot. And do all the trucks of the gen have the same size bearing for it? AutoZone shows. Couple sizes