67 Dart, 7" for 8 3/4 Rear swap- Driveshaft alterations-

-So I have a stock 67 Dart, 225 Slant Six Automatic Transmission.
I recently pulled out my stock 7" rear and put in a 8 3/4 "A" Body rear w/ 323 gears, big bolt Moser axles and so although I thought this would be a simple swap but soon realized my stock driveshaft is a bit too long. If anyone has done this swap like this can fill me in on what type/length of shaft I need as a new replacement- that would rock. Thanks much.