As far as hydrogen generators are concerned, don't waste the time and effort to do it .
If the R65 engine draws in 100 cubic feet of air a minute at highway speeds, the amount of hydrogen required to make any measurable difference is far beyond the capabilities of the typical hydrogen generator .
When a home built generator is working properly, you get a small amount of gas bubbles out of it, about the same you get out of a flooded lead acid battery when you charge it .
I think I saw that you would need about 15 % hydrogen in the air going into an engine to make any difference, so you would need a generator to produce 15 cubic feet of hydrogen a minute, the amount of water you need to carry would be more than your fuel tank .
I had a co-worker try this on his truck, a waste of $500 in his case .