I'm working on a 26" conversion using a Schwinn Varsity. standard 126mm rear hub and 100mm front hub spacing.

There's no brake caliper with long enough arms to reach, and if it did the arms would be so long they'd be like noodles. I considered a coaster brake, but I really wanted at least a 5 speed cassette. My solution was to go with drum brake hubs in the front and rear. I got a Shimano 7 speed rear hub with a Drum brake, and a Sturmey Archer Dyno&Drum Brake hub in the front. They're laced to 26" Sun Rhyno rims which are going to wear big fatty 2.125" balloon whitewall tires.

The drum brake hubs are cool.... i got the rear for 30 on ebay but dropped 60 on the front dyno hub...you could get a front drum brake hub without the dyno for 45 new.