Does Ok Model engine Company still sell engines?
Actually COX had better marketing on their side. When I was younger, Cox had glow engine products in just about every store in the USA and probably Canada too. I remember even the local big name pharmacy even had some Cox products for sale. Cox had packaged RTF control line planes with everything needed to fly, and had small pint and quart fuel cans being sold everywhere too. Cox managed to out do everyone else and get their engine products being sold everywhere.
The main problem was the Cox engine was easier to make and thus could be made cheaper. But as the marketing wars went on, COX had a huge economy of scale going, where they were making probably thousands of engines a week. The other manufacturers were likely in the hundreds of engines in a batch a few times a year. They never got into the huge mass marketing like Cox did.
The Cox Tee Dee wasn't the only high performance .049 engine around a long time ago. The FOX .049 FAI engine ran just as good as the Tee Dee and was arguably maybe a little bit more powerful. The fuel tank was a option.
It used SPI sub-piston port induction too.