Re: SM420 to Dana 20 adapter?
The bolt patterns are the same for all Dana 20's but the spline count on the input shaft is what varies from Bronc's to Scout to Jeeps. I think Advanced adapters can put almost anyD20 to your tranny advancedadapters.com. And yes Bronco 20's have 2.46:1 low ratios same as a Dana 18.
Scott C