it is hard to say, I don't think so. But the engine was a 1975 design large case engine. it first came out as a .40, then later they bored it out to a .45 and it was offered as a .40 and a .45 for a long time. The first engines had the shiny silver aluminum look to them. Later Fox started bead blasting the engines to give them the gray color look. I think that was in response to the Japanese engines at the time having the bead blasted gray look to them as well. The early engines had the two muffler mounting holes about 2mm closer together than the later models did. So you couldn't easily use the newer versions mufflers. Then in the late 1980's or early 1990's Fox came out with the .50 engine. In these cases they simply kept boring out the engine crankcase to accommodate the larger cylinder sleeves (and change to the head button of course), but everything else stayed the same. Later as the molds wore out, Fox changed the molds to what we see today with the engines. They incorporated the side port on the engine better and opened it up more, so it didn't have the "wart" like bulge on the side. I have some vague memories of Fox changing the crankshaft and stuff when the molds were changed on the newer ball bearing engines, but I can't be certain. I haven't tried to mix and match the parts on the engines yet.

Now in the late 1970's and early 1980's Fox did manufacture a lower cost bushing version of the engines. This engine had a smaller crankshaft and it had a smaller crankpin as well. The connecting rod was more thin and not as wide as the ball bearing engine crankshaft. It also used a slot to help provide oil lubrication, whereas the bal bearing engines had a hole drilled in the rod for that purpose. Fox might have timed the engines a little different, but I think any timing changes was due to the smaller crankshaft having a smaller intake port hole in it.

I think the .50 engine might have been on the cusp of being too large of a bore as it impinges on the port passages making them smaller, which would affect how much air fuel can flow through the engine. The .45 was pretty close to optimum, but maybe something like a .47 or .48 would be the ultimate size to go with. So the .50 could be a bit flow challenged for higher RPM running, but it can take a larger prop than the .45 can.