Aluminum versus iron when buying used LS

[Sovereign]

If 600hp is the goal and you want mildish street manners, you should stoke the engine in my opinion just as Accelo suggested. I would also say starting with either a Gen 3 or 4 will be fine as you'll need aftermarket or factory ported heads regardless. Basically, you need to start with a block that has a 4.0 bore. Everything else will be bought new. The reluctor wheel issue can be corrected if it concerns you.

If you lower your goals to 500hp, life will be cheaper, easier, and more manageable.

Since I don't know you or your car history, do you have any idea what driving a 600hp vehicle is like with no traction aids? If not, I would suggest stepping back to no more than 500hp or, honestly, 400hp until you get used to it. Modern engines along with fantastic modern traction aids give an incredibly false sense of what it's truly like to manage 500 and 600 hp. I can assure you, a stone stock LS3 in a C10 that can handle and brake will be a riot to drive and be easy to live with.

Sounds like it's going to be a fun truck.