"The Mowercycle" a microcar road legal trike

I'm leaning more towards a trailer wheel or similar. The hardest part is making sure the wheel fits a common highway tire size. I've found cheap go kart brake calipers, which will be good enough for now. I can machine my own spindles better than what I've seen on go kart parts websites, and I can make brackets for a disc brake to mount up easily enough, and probably the disc too. I'll have plenty of time to do that this winter.

Oh, on a positive note, someone identified my engine as a 16HP briggs flathead. That explains the large torque at low speeds. That's plenty enough horsepower to get me to highway speeds without any trouble. I also have a close enough model number to get replacement parts if I need them.

Gotcha. I’m putting trailer spindles/hubs on my rig also…once I get around to it.

Oh ya an old cast iron 16hp B&S is more than enough! I have one, it's a 1977 model 326434 0023-01 and same as yours has a starter/generator. Is your model and date code not stamped on the top of the fan shroud?

Nah, all identifying marks and nameplates are long gone. Only thing left is the briggs symbol pressed into the blower shield. I haven't taken the cover off so I don't know if there's any information on the flywheel.

The starter-generator wasn't on the engine originally. I added that.

Should be stamped into the steel fan shroud probably somewhere under where you coil is located or on the curve under the gas tank.  In your case, the starter which I believe was a plate that I see was removed on yours. I'd still check under the coil. Maybe get lucky.