I can't say for absolute certain that that is not the original engine for that machine. It is of the correct vintage for your machine (I.e. Early to mid eighties). The point of confusion is that the frame appears to be a Tractor 8 frame. That said, the parts data I have (which is the same as that held by ODK) doesn't cover some of the mod status that is on your machine because your machine was produced after the catalogue I have was printed. A newer catalogue would be handy. Point is, Greenfield made changes all the time and I can't say for certain that this engine wasn't original on this machine....but if you asked me to bet a 50 dollar note on it I'd say it's not the original.
It's always difficult trying to figure out an approach when in a situation like this - two engines and both an unknown quantity. Perhaps a suggestion is to spend a few more hours working out if the black one might be a goer. If the coil is no good on the black one then check if the red one has spark. If it does, pop the coil from it into the black one and take it from there and build up the black one from the bits you have from it and the red one. What's the worst that can happen?
Whichever you decide to try to get going first, you need to have a plan and stick to it.
