The engine codes of the 40’s are starting with one digit and a dash.
Like below.

1- ****** is KDF and Beetle until 1956
2- ****** is Kubel
5- ****** is Type82E
6- ****** is War time industrial
7- ****** is typ7 Schwimmwagen

Engine code starting with an A is for Austausch or Exchange.
Engine code starting with KDS is a Swedish Factory Rebuilt engine.
From 19-01-1951 the casting of the crankcase is Magnesium instead of alloy.

The very early KDF crankcases can be recognized by missing the top cross crankcase bolts.

The pre 1950 crankcases can be recognized at the length of the oil dipstick.