[garyd1961]

You can't beat the GM Vortec Crate engine. I got the 12530283 with 4 bolt mains. It also has hardened valve seats inserts and sodium filled valves which are designed to run cooler. It does come with a balancer, valve covers, and oil pan but not the water pump. One thing some people over look is you need a melonized timing gear not a melonite coated gear.
The Summit Stage 1 intake is perfect for these motors in a 4000 truck. Also don't listen to those who say you should change the factory cam. The factory cam was designed to have low end torque to give a heavy pick-up the power it needs to get going and to give it pulling power for heavy loads. With a good four barrel and headers you should have 300 net hp easily. That would be like dropping a 350 with 350 hp (gross hp)in your truck back in the day when these trucks were made.
If I didn't want headers I would get some 2 1/2 inch ram horns. I never liked headers myself but I already had a set for another hot motor I had in my truck so I used them, now I like them. Just use good gaskets and retighten the bolts after the first run and motor cools. I actually tightened mine while the motor was still hot and rechecked them after it cooled.
These motors are made in Mexico but don't let that bother you, they are GM motors.