David,
Those are wonderful engines, and perhaps the best general purpose half A engines ever produced. Their only fault, is that they can be very difficult to start when new. Spring starters help, but many of them came without the spring. The good news is that all of the Norvel engines have a steel thrust washer between the drive hub and crank case, so an electric starter like yours can be safely used.
Break them in exactly as recommended in the instructions, and they will last a very long time. Use smaller props to allow them to spin up rapidly, as the fuel draw is marginal with that big bore venturi.
I'm not familiar with the numbers you mention, but here is what I know about them (thanks to Geo Bain for his clarification).
They come in two different porting arrangements, and two different cylinder types. The only way to determine the porting arrangement without paperwork, is by removing the head for visual inspection. The sport tuned engines have five small ports (plus exhaust), and the high performance (AME) tuned engines have three larger ports (plus exhaust).
My early .049 is a Big Mig sport series, with natural aluminum fins, and a smaller glow plug. It also has a brass needle valve, without the right angle needle extension found on all later steel needles.
Revlite engines have larger cylinder fins that are black anodized. The cylinder mounting screws are hidden by the head and fins, and only accessible through holes drilled down through the fins.
The earlier (non-Revlite) cylinders have aluminum fins, and semicircle screw driver clearance cuts milled into the fins. The screws are plainly visible at the cylinder base, and can be removed with the head in place.
I'm not sure if the high performance AME tuning was ever available with the early aluminum cylinders, as I've never seen an example.
Later Norvels went to a hotter plug known as the Freedom plug. The earlier plugs were probably OK for C/L use, but too cold to give a reliable idle with throttled engines. The early plugs are smaller in diameter, so the Freedom plugs will not fit the old head clamps. The old head clamp part number is 100131, and the new Freedom plug head clamp is 110131. The new head clamp fits the old engines, as long as you use a Freedom plug.
Norvel also made a glow plug adapter for regular glow plugs, but they only fit the older p/n 100131 head clamps. I have one of these, but have not tried it, and don't recommend them. Use Galbreath glow head adapters, with the excellent and inexpensive Nelson plugs instead. Norvel plugs are getting very hard to find.
Probably more than you wanted to know.
Bill
PS. If you still need engines for the kids, I've got a couple of Cox Golden Bees that your welcome to. They look very clean, perhaps even unused, but I've never started them. One is missing the prop screw and washer, but both have tanks.