Correct Bottom Bracket for a 1991 Cinder Cone???

[FluffyChicken]

Go for it.
On the off chance it doesn't work out you should be able to sell it on without too much hassle.

I think Suntour Cartridge Bottom bracket (same style as the UN series your looking at measured about 126mm for none MicroDrive cranks.)

So 127mm would again be fine.