The cartidges (center section) are the same. Turbine and impellar wheels are different. The H1C tubine wheel is way too small for an HX40 housing- you'd get no spool at all with an HX40 housing on an H1C wheel.
Now, if you had a good HX40/H1E wheel and shaft, I see no reason not to put it on a HX35/H1C cartridge, depending on which one you had. Actually, I dont think the cartridge would make a difference til you got to the impellar side.
Daniel