Mailman brought me this 1987 Suzuki DS80 motorcycle fork I got from ebay:
Similar to the popular Suzuki K10 fork, minus headlight mounts and fork covers. Thankfully, this dirt bike stem is 1" diameter and it slipped right into my cruiser frame headset. It's 1" too long, so need to cut & rethread the stem and install correct bearings.
For mockup, I bolted in a 26"mountain bike front tire. Skewer was too short, so I used the rear axle one. The triple tree is 4.8125" wide, 14.625" from axle to bottom of triple tree bracket. The DS80 OEM front tire is 2.50-14, or 19" diameter. I'll use a Dunlop 404 motorcycle tire. It is 3.15" wide and 26.67" diameter. If I don't cut the stem, I'll have 3.58" fork travel before bottoming out. Sidewall clearance is .81" per side, which is a LOT. On my Rockshox fork and Schwalbe 2.35", there is .25" side clearance. The Schwalbe tire would have 1.21" sidewall clearance per side in this DS80 fork..
This tire is a MONSTER. It is the OEM front tire for certain Harley Davidson bikes: