I understand that it is hard to find a mountain bike w/ horizontal drop out and the earlier 80's vintages may have this drop out.
It also sounds like it is expensive to get the adapter for the rear wheel.
Besides these to points I'm trying to sort out the pro's and con's of road bike, vs. mt. bike fixed gear set ups.
Potential advantage of Mt. frame to me would be:
1. Higher ground clearance for bottom bracket. (might range from .5 to 2 inches higher) to help keep pedals from scraping.
2. relaxed geometry may be more comfortable for some.
1. More weight
2. May have problem with limited fat tire selection, lower pressure and much greater rolling resistance.
Can 700's be put on mt. bike.
I'd appreciate any feedback/suggestions from someone who has made a fixed gear bike out of a mt. bike.