oldkart,
I have not seen anything Hodaka that would work in the kart engines I've worked on. Just so happens that I know a guy that probably has one of (if not THE) largest collection of Hodaka stuff in the country. Tons of original parts, many still new. I've had the chance to dig through a good amount of the stuff in his shop, and nothing had the right combo of diameters/widths/lengths. Even he is struggling to find certain size/length rods to rebuild some of the more obscure Hodaka engines (like the 175cc they built).
That said, I think you are correct in that probably most of those original Japanese engine con-rods were probably forged by one or two outside companies for all the manufacturers. They have that certain..... look.... this is fairly unique.
As far as longevity... I had no problem wadding up the b/e rod bearing on my modified 125cc Yamaha flat track bike back in the early 70's, LOL. That was on Klotz, and I haven't touched the stuff since! Went to Green Label Bendzall back then, and never had another issue. The revs we see in kart engine surpass anything I've seen in a comparable displacement bike engine though... and I'm guessing the abuse the rod takes probably goes up by the square of the rpm, or something like that.
PM