You would be money ahead to just find a used H model and buy it. I tried to convert my G to a H. By the time you buy parts to convert it you would be in the hole. The base plate in it's self is completely different.
I once thought of doing this to a Hyd. Mec Hustler, before the 9000H, and was told just the same as CalKidd. It would be less costly to find a used 9000H. They are on here all the time for sale you just have to watch and be ready to buy. Deals can be made.