The question of pitch..
The question of pitch is really the question of required HP vs. available HP and what RPM you want at what altitude for a given speed. We specify props with a geometric pitch measurement, usually at the 75% radius station, but that's a very rough way to get at the real/effective pitch which some also call "advance".
If, for example, you want a given airplane to use 2700 rpm at 8000 density altitude, WOT, you must know something about the power and drag. If you don't, then you will get the pitch correct only by accident or luck. Craig had to re-pitch mine (more pitch). He got it right where I wanted it on the second try, but it costs him $$ to do that and it takes a lot of the builder's time, too.
The required HP is the THP that your airplane needs for a given speed at a given density altitude. This can be closely estimated with the methods I developed and which are explained on the pages linked below.
The available BHP is a little harder because it's tied into your (unknown) propulsive efficiency which is part propeller efficiency and part propwash-airplane interactions. That said, if you know what the airplane can do with an existing prop and can estimate the THP as above, the right answer can be narrowed down considerably. It is nice to say that for a given RPM and MP a Lyc-type engine produces X BHP, but it really isn't all that accurate. If it were, there would not be so much variation between charts. In reality, the manufacturers are not consistent about how they measure BHP in the test cell, so they may be exaggerating for effect. Or not. For example, it is not very accurate, especially with RV's, to use 75% of rated power at 8000 feet.
If your new prop is more or less efficient than the old one, then for a given speed and altitude, assuming to can reach that point, the rev's will vary accordingly.
I am willing to assist VAFers with the use of the spreadsheets, linked below, in order to assist with telling Craig (or any other prop maker) what the requirements are. Online or offline. It can't hurt and it might help.