My experience with engine builders and machine shops is that it is difficult to achieve a good experience without an ongoing established relationship. The reputable guys are always busy and the first red flag is a builder who is willing to immediately start work for someone they don’t know. That would be me in just about any of these scenarios.
I kicked around the idea of going for a 383, but decided against it at this stage.
The ZZ4 chevy 350 short block, direct from gm performance is the block that major engine builders such as Edelbrock use to build their own motors. They produce a known, new, not rebuilt solid foundation that out of the box reliably capable of producing up to 450 horsepower. Short of the need to build a race engine, it’s hard to beat for the cost. As a 4×4 motor, I have no intention of trying to coax 450 horse out of an engine. I don’t want to sacrifice low end torque by maxing the horsepower. I will avoid high lift cams. My goal will be to maximize the efficiency and torque of the engine. The ZZ4 4 bolt main block is about as ideal as you get and at less cost than a reputable machine shop build. As a 4×4 rig, first and foremost I want reliability, that rules out bargain basement question mark short blocks from volume builders too.