You've probaly got an aftermarket crossmember for the rear mount, if bolted, you can just simply move it back the required abount. The driveshaft would be best done by a shop that specializes in those. You'll need to get the dimnsions once the trans is in the truck to be accurate. You should be able to find a driveshaft shop by either talking to the people at the auto sparts stores, machine shops, or possible at the local race track. They can guide you someone that does the best work. Dpending on what's available, sometimes it's actually cheaper to get an entire driveshaft made that have one shortened.
