I have the nv3500 out of my blazer and I have to replace the shift fork. The only problem is that it is stuck in 1st. Does anyone know where I can get a 1-2 shift fork??

 

Just did a quick search and found this site... Not too much as far as design goes, but lots of info:
Getrag HM290, 5LM60, NV3500 Truck 5 Speed (RWD) Manual Transmission Parts - Drivetrain.com

Looks as though you are going to have to measure the ID of the shift rail to get the appropriate fork.