I'm doing the same thing....building up a 599 6.5 from salvaged engines.
Maybe someone who knows could clarify what all the stampings on the bottom of the block means. I know some of them relate to the piston sizes which were fitted at the factory. I think some also relate to the size of the crank bearings. GM offers different size main bearings to get the oil clearance just right.
I have salvaged 5 engines from dealer dumpster diving, and saved all the parts which looked OK. (I got permission first)
So I have a collection of precups, with 4 different sizes and shapes of holes. The largest is about 9/16" out of a '93 TD. The smallest is about 3/8" out
of an '83 6.2
I have heard that the small cups are better for economy. Maybe they'll fit
in the later heads, I don't know yet.
One thing I'd like to do at this stage is drill/tap the block for a relocated water jacket drain on one side. The boss on one side appears to accomodate a relocated drain (the engine block drain on one side is inaccesable because it is behind the engine mount). Anybody done this?
The '83 block I salvaged had the cooling passage around #8 totally blocked with crud. I cleaned it out by putting some 1/4 steel tubing in my pressure washer and sticking it down in the head bolt holes. No wonder the head cracked at #8.
I started spending money on my project with this '83 6.2 block before I was aware of the stronger 599 lower end. Since the '83 will be built (now at 030 over) for economy, it should stay together. I bought new pistons and had the rot. assy balanced so far.
Any assembly tips for making the bottom end on a 6.2 (non599) block
stay together over the long run? Balance for sure is the main thing.