i understand needing the cogs to be parallel with the chainrings and that there is only so much side-to-side latitude the chain can absorb in its travel from low to high cog & chainring combinations.

one of my down the path questions will be if i can change chainring & cog thicknesses to use a barrel link type - maybe "modern" is a better word - chain.

the original chain looks like it could power a mini-bike with a Briggs & Stratton engine.

that must have been when i was in my delirium because i don't remember that. i did measure the existing factory rear dropout inside to inside and came up with 125 mm.

i don't even know what O.L.D. means.

but i can certainly imagine what having the rear wheel off the frame centerline means : Trouble