I have a 1990 Chevy 2500 2wd drive truck with the 350 5.7l v-8 from a 1995 With a manual trany. Here is what I am looking to do replace engine with a better v-8 or diesel. And make it 4wd. Any sugesti

Or should I just rebuild engine I have and swap tranny? Just looking for ideals.

OK. So right know you have the '95 350 with a manual in the 1990 truck. Swapping a diesel in will take time but doable as the 6.5 was available in the 1/2 ton during the 90's. The 4x4 conversion is the issue. The GM trucks have different frames between the 2wd and 4wd. The easiest route would be to convert the front to a solid axle with leaf springs. Since your truck is a 3/4 ton it should have the 8 lug bolt pattern on the back.

From there there is two choices. 1.) Find a '87 or newer truck with independent front suspension and 4x4 with the same manual tranny and install that transfer case with a dodge or ford 8 lug front axle with a matching ratio. This will give you a drivers side drop front driveshaft. Just confirm the rim backspacing before finding a matching set (I know most dodges and GM rims are interchangable for 8 bolt). Or 2.) Adapt your manual to an older GM t-case (205 if you can) and use a GM 44-HD or 60 from any 3/4 - 1 ton solid axle rig. Passenger side drop for front driveshaft.

As per the diesel. What will the truck be used for? If you build your 350 right you can match the 6.5 on everything but fuel mileage. I noticed that you said in the first answer "swap tranny" the the 1990 manual or auto. If your swaping from auto to manual you will have to modify the wiring harness and change the ECU chip to a manual assuming you keep the EFI and go with the 350.