Proptop, the Alpha is not the .455 TPS engine. Rather, it is a .40 that uses the same carb, cylinder, cylinder head, crankcase, and backplate as the 46NT. The 46 is actually a bored out 40 with a longer stroke by way of the crankpin placement on a different crankshaft with a longer rod. The 46 liner is thinner, so that's the larger bore.

The .455 is a totally different engine, and to confuse things, it has an 'a' on the cylinder head for decoration. I've bought 7 or 8 46s and own a well used .455 that I love. It is my favorite 2 stroke engine.

Periodically we need to mention that Evolutions, at least up to the last year that I'm aware of, all run terrible with OS 8 glow plugs. These are too cold. The Evos need hotter plugs.

BTW, since the 46 is actually a 47 you are better off using the 40 crankshaft and shorter rod because it is better balanced over the 46 crank.