The forks are 15+ year old mountain bike triple forks i bought on ebay in 2003 or so. I had to cut down the head tube and modify it to fit a 1 1/8 mountain bike headset, and then i just fit it up. still needs adjustment, but its really solid and lightweight.
The rear tire is from Treats, NR-77 14 x 80/90
But the engine/trans is from an nx50 (express-SR) and the rear wheel is from an urban. It all just fit once i took out the starter motor and trimmed the dust ring around the rear brake so the wheel sat all the way on the spindle.
Dirt tires are generally wider than street, on account of the dirt nubbins, even for the same "rated" size.