http://www.combinedfleet.com/ijna/ijnaf.htm
This where I was able to locate some speeds. You have to get away from the thinking setting 80% and 80% is the best.
Prop pitch controls rpm, power also controls rpm. Lets take the Ju-87 for a moment. The aircraft guide with game says cruising is 2100 rpm. (I know you didn't ask about Ju-87, just using it as example) So lets say I am at 100% power and I adjust prop pitch to whatever % I need to give me 2100 rpm. Now If I reduce power I will probably need to increase prop pitch to maintain cruising of 2100 rpm.
Also you loose power with altitude so you have to make adjustments there as well.
Basically what I am saying is that there is no set 80/80 or whatever generic setting that will always give you perfect engine setting for every plane. You have to figure out what speed you want and adjust manifold pressure and rpm as necessary to maintain that speed. Learn to read your gauges, will tell you all you need to know.