Gents,
I've had a thread in the classifieds section for these for a while and have only had 2 people asked to be placed on a waiting list for a production run of these. Quite surprising on one hand given they are out of production and quite popular. Also not surprising as the original parts last so well.
I have a good sample engine that has been loaned to me in preparation.
I think you more-or-less got it above. One other thing you might not fully appreciate is that, at least around here, more people ran the 61 rather than the 65. This was due to the former FAI 10CC rule. As soon as that got changed, Randy/Henry went to the 65, but not too long later, there was a 75. Most people still running IC are running the 75, for good reasons. I am probably the last person running a 61, it's a RO-Jett and it also doesn't wear out or need replacement parts.
Some of the others are popular due to identified serious flaws (like the ST46) and for whatever reason, people are still trying to run some of these older engines. PA/RO-Jett, 40/46VF (for which there is already an AAC piston/liner, and the originals are nearly bulletproof), those are mostly specialist engines that only the few remaining top contenders still on IC would be interested in, and that is a very narrow market.
As you note, the originals don't wear out under normal use, so any interest would be if it ran differently somehow, and most people will probably figure it runs well enough now. Any alterations I or someone else might suggest are, as far as I can tell, much different from what you would want to do otherwise, and would be highly speculative, and say, Todd might want one thing, Derek another, Brett another, all conflicting with each other.
I think everyone appreciates and admires your efforts and the products seem to be of extraordinary quality. But as viable business suppling such a niche and contentious group, I don't see it and I am not too surprised that only a few signed up for it.
Brett