All very impressive. I'd say the builders all seem to be imaginative. I think it also takes some courage to make such modifications. I know, from experience, it can be disheartening to spend a huge amount of time trying to scratch-build something only to have it not turn out well. I believe practice is the only way to get good at scratch-building though.
I know a little about machining and guestimate you'd be looking at between $50 and $75 per wheel. Also, at that rate, the machinist would have to agree to do the job for love of the hobby or a personal challenge. After I realized how expensive it is to have custom machining done, I bought my own lathe and mill and derive a great amount of satisfaction producing my own metal parts.
Interesting project Dave. I suspect many would like such an engine considering its use in the vintage of trucks represented by available kits. Were there significant physical differences between the mechanical version and electronic version of the engine in question?