Speedometer question 2wd to 4wd...

i am changing my 91 (electric speedo) MJ over to 4wd. I am using a 96 AX-15 trans and T-case. The truck was originally a 2wd AX-15. The plug on the 2wd tranny was a 2 pin plug and the plug on the T-case is a 3 pin. The wire runs up the pass side unifrane and up the firewall to the main harness. It is a 2 conductor cable. What do I need to do or get to make my speedo work again??? Please help! I hate to drop all this money on the 4wd only to not have my speedo work, thats annoying. thanks -J

Not sure but.. can you swap the plug? Do you have a FSM? Maybe splice in the connector for the newer stuff?