well i think my nv3500 is crapping the bed finally with over 250000 miles on it cause it makes a whine when i let off the gas its either the main shaft bearing or the syncros so can you guy tell me what my options are can i use a gm nv3500 out of an s10 or should i just rebuild mine let me know please.

 

NV3500's have cast bellhousings so one from an S10 will have a cast SBC bellhousing. The guts out of it should work (and you'd get a "better" 3.49-1 1st gear out of an S10 trans, easier than finding a Mopar NV3500 with that gearset).

I'd say rebuild yours and run it 'til the wheels fall off.