The earliest .40 and .45 high back engines used a exhaust muffler hole spacing that was approximately 2mm more close together than the later engines had. Fox changed it after the first initial production runs.  So yeah finding a original early style muffler is a problem for them. But that early muffler wasn't all that good anyway, so it wasn't a big loss to not have one to use. About the only place that early muffler works good is for a Fox .45 diesel conversion. The diesel conversion doesn't result in a huge power loss from the muffler being so restrictive. Plus the diesel is more quiet than a glow engine too.  But what I did was make bridge adapters to convert the odd exhaust screw width size to some other size to fit a better muffler on the engines. If I remmeber right, at the time that Fox manufactured these engines, mufflers weren't a required item per se, so Fox wasn't including mufflers with the engines at the time. But it wasn't long afterwards that mufflers were being included though.

Now as to the connecting rod, there were two different main types, a smaller more narrow in width one for the bushed crank engine and a larger one for the ball bearing engine.  Now I do not remember if Fox changed the crankshaft size any with the ball bearing engines, but there is a good chance that the current rod would work with the older engines.  The bushed crank engines is another story though. Fox made the crankshaft a little smaller and the rod looks similar but is less wide as the crankpin is more short. The rod also had a very narrow slot cut in it for oiling the crankpin. But I think that one could file the rod down some to make it less wide and it may work. I have vague memories of messing around with that and then I found a rod, so I didn't persue it to its conclusion to see if it would really work OK or not.

I still have several of the old silver colored Fox .40 and .45 engines myself. Way back in 1978 when I visited the Fox factory I bought a bunch of engines from him in their small store inside. I am still working on trying to wear them out even today.