Let me see if I can confuse you a little bit. GM Performance Parts, I think, used to be a product line sold by the dealers. GMPP is what you bought if you were building a hot rod and wanted a special engine. GMPP included "performance" parts, cam shafts, fueler heads, high horsepower engines and parts. You could buy a duel quad set-up for your '57 chevrolet with a corvette motor and you would be buying GMPP items. On the other hand, GM Goodwrench was a replacement engine. Stock, just as it came from the factory.
I'm looking in the Jegs catalog and I see engine P/N XXXX8758. This is the standard replacement engine for your truck and year model. On the other hand, you could spend more money and buy a GMPP ZZ350, or a GMPP 350 fast burn engine. Those are non-standard engines. They would require a little modifying to accept your TBI system and all the sensors, etc. In my '88 GMC truck, I'm on my third engine! And the second P/N XXXX8758. The first replace engine lasted 34K miles, and the Chevrolet dealer replaced it for free.
Getting back to your question of where to buy. I've bought a lot of stuff from Jeggs and they've been great. I've ordered the wrong part number, and they replace no-questions. I bought a set of AFR aluminum cylinder heads, which are made in Calif. where I live. But because I bought them in different state, Ohio, I didn't have to pay sales tax. For buying a crate motor, Jeggs is cheaper than your local Chevrolet dealer. Just make sure you have some way to off-load it from the delivery truck. A forklift?
If I bought another engine, I'd look around for something a little more powerful. But you still have to use your TBI system. How about a "long" block from Blueprint? A 383 from BluePrint? They have a lot more engines than just what you see in the catalog. Jeggs will sell you anything made anywhere. You find what you want, and they will get it for you. Hope this helps.
