ZZ4 is a reproduction based on the old H.O. 283 Motor. The ZZ430 was a very Limited production ( Duh 430 units ) High Output Small Block. When you consider what your getting with the ZZ4 it's really not that bad a deal. Besides, you get a warranty..
The ZZ4 is the foundation of all of GM's performance engines. It used to come with a Nodular crankshaft, powdered metal rods, and hypereutectic pistons. About 2 years ago, they changed the crank over to a forged unit and left the PM rods and Hyper pistons in there.
Any of these engines with the ZZ4 shortblock are excellent choices.
The ZZ430 uses the same short block but has the GM Fastburn aluminum heads, aluminum intake, larger roller cam. Like said previously, the production number of the REAL ZZ430 was 430 units and they were rated at 430 hp. The ZZ430 was typically sold for between $10,000 and 12,000; they are now worth more as they are considered a "collectors item".
Currently, there are people making an engine they call a ZZ430 but it is not the GM built one. I think Pace and Scoggin Dickey both offer their versions of it. My friend runs a ZZ430 with an LT4 Hot Cam kit in his 1986 Z28 and it is unbelievable. It has to run somewhere in the neighborhood of mid to high 11's on just the engine. On top of that, he has a ProFogger on it; we figure on the spray it should run 10's. Yes, the car is driven on a daily basis and he shifts at 7,000-7,200 rpms and it is STILL PULLING. I am getting ready to do a video of his tach on a run for the non believers on the 7,000 rpm thing.
Here is a picture of the ZZ430 clone my friend built. Notice the lack of belts!! We custom fabricated a mount for the alternator to be driven off of the end of the crank shaft and the water pump is a CSI electric unit.