I'd put a 180 thermostat in there if I was you. As well as a fan shroud. A 4 core radiator would help to. NV3500 is a good tranny...little closer ratio then a SM465, but you'd have to swap to a hydraulic clutch far as I know. NV4500 is perrty much the same gear ratio as the SM420 and 465 but has another gear and is smoother shifting. NV3500 has a low first far as I know...but its rated at less ft pounds torque, which I'm sure you'd be fine with that 283. If yer gonna be using the truck to tow and haul..I'd say a NV4500...just for the fact you have the super low 1st...and the 5th gear..but you would need an adapter(I believe) and there are two different 1st gear ratios on these...1993 version was 6.34.1 and from 1994 on it was 5.61.1. I'm not sure if the 4500 had a manual clutch option. I'm sure others know more about then me. Hope some of this helps.
