I would also ditch the NV3500 as a 350 VORTEC can eat one for lunch, let alone what the torque of even a mild 6.5 can do. As for teh wiring, trhere really isn't much to it for a manual. You should have a temp switch on the engine that engages the high idle and cold start advance, a 12V+ for teh fuel shut-off solonoid, and then the glow plug controller which can be hooked up and manually activated when needed.
1995 GMC 2500 SUBURBAN powered by 01 DURAMAX/ALLISON, 3.42 gears, 261 T-case
Trans has a mild build with ALOT of help from MIKE L. which included ALTO's for C1-C4 and a PI ML converter
DIAMONDEYE 4" exhaust with a CORSA muffler, AFE stage 1 dry filter, EFILIVE, KENNEDY single pump and pump rub kit.