@legofiddl3:

Does anyone know if there are any issues with intergrating weapon development back into Spring 1942?

I was thinking of just using the standard revised rulebook found on the axis and allies website.

You can use these, from AA50 for AA42:

http://www.boardgamegeek.com/filepage/56883/tech-chart-and-rules-1942-v-1-4

http://www.boardgamegeek.com/filepage/56867/tech-tokens-for-aa-1942-and-other-aa-versions-v-1