Driveshaft ?

[Ta2Don]

I'm building a 65 short Stepper, and as part of my build I am installing a NV3500 5 speed which is 3 inches shorter than the TH350 that was in the truck when I purchased it. My question concerns lengthening the driveshaft. There are a couple of places locally that do this type of work, and I've heard good reports about both shops. The question I have is, Do I need to go with the shop that is going to replace the entire tube, or with the shop who says they can just add the 3"? There's about a hundred dollars difference in the estimate so I'm looking for advice since I've never had driveshaft work done in the past. Thanks in advance...