When you think that you are taliking of Military Engines. They are built to run on any C*ap you get to put in the tank. 101's for instance use a low compression version of the V8, I never had any trouble running it on unleaded. The Dodge, the problem is the modern fuel is to goo for it. An electronic ignition gives much smother runinmg. As for Catalyst's. I've used them for years on all sorts of vehicles. The same three, two pellets in mesh , purchased about fifteen years ago, one tube one slavaged of a Range Rover. My empirical experience is that they keep fuel fresh and drop exhaust emmisions. Apart from am old Montego, according to manufacturer could not be converted to run on unleaded in any form (Why I purchsed the original catalyst) this engine dropped a con rod, after the sump gasket started leacking but had run about 70,000 miles on unleaded. The vehicles have always been scrapped for other reasons than engine wear.