I am going to nominate my 1968 Wheel Horse commando 6. I bought this off of Craigslist last fall. I'm not sure what everyone considers original, So I'll put it up and if anyone has objections I'll go ahead and remove it. I have nothing to hide and I'm not trying to fake anyone out. It is as original as I can reasonably make it until I find the parts. I did nothing cosmetic to it, just basically put it back together and made it work.
When I brought it home, it had a replacement 8 HP Briggs engine. Thankfully the PO didn't hack up the hood to install it, he just left it off. I found an original condition Tecumseh HH60-105047 engine, also on craigslist, that came out of a slightly newer Wheel Horse. It was missing the governor's internal parts as well as the external linkage and mount, the carburetor, the fuel tank, and the air cleaner. I had also bought a second engine. It was an HH60, but of a different era and purpose. I used all of the governor parts from it as well as the muffler. I had a carburetor lying around the garage that just happened to be the right one for the engine, but I had to buy new throttle and choke shafts because they weren't the right type. The fuel tank and mount I found on E-bay...in original condition. The air cleaner is off of a Kohler engine, but it fits without modification and looks like the original Wheel Horse type that came with the tractor when new! (makes you wonder if that's not what Wheel Horse did originally) I also installed a new drive belt (OEM from Toro).
There are only three things that are not as originally supplied. I had to use the throttle linkage off of the other engine which came from a tiller and therefore had to modify the choke linkage setup to work properly. The second thing is that I had to buy an ignition switch (OEM from Toro) and it was expensive! The original design called for the starter current to go directly through the key switch. I installed a solenoid so that I wouldn't be replacing that switch every couple of years. The third thing is the muffler is not like what was supplied by Wheel Horse.