HK3P G23 lower frame is the same as G19?
 

Still searching for a WE G19 lower frame with Glock trades, almost impossible to find but there is available HK3P G23 (semi/auto). HK3P is knowns as WE with correct trades. Is this G23 lower suitable with G19 slide and internals?

Well if it's the same case as the g17/G18 then yes it should be interchangeable. Reusing the internals from the stock frame.
Assuming firstly that the 23 and 19 have the same size frame (i don't know all the glock model well) and secondly that the "rumors" are true and the hk3p guns are in fact trademarked WE guns lol