If the head were shaved, wouldn't some part of the valve train be of different dimensions, such as push rod length? Perhaps the combustion chamber itself is just cast smaller.that is correct but I have not found any info on the CR for the propane 49G. It is most likely simply be a shaved head as the head has a very deep but small chamber. The piston comes to the top of the bore and only the gasket thickness separates the piston crown from the head. Piston P/N was the same for the 49G, 49M, 49S & 49T. The 49G has a unique P/N for the heads, all other models are using either the Professional or the Vanguard heads (Vanguard has better quality valves, no other difference).
As the generator engine has the lowest forces of all applications (no side or thrust load, impacts etc), the bulk of the engine will be Professional/Commercial standard.