Where are you seeing these options?
Links to both?
I don't have a light 250 with a semi-floater.
I would have thought "flange mount" would be the D60/61, where you have to pull the axle to get the drum off?
Unfortunately, Gary didn't seem to get to the correct parts list for your vehicle.
Edit, id be willing to bet that this one, that's fits 8.8 & 10.25 w/ 2 1/2" shoes is correct.
Though I don't think I've ever seen an 8" w/ 8 on 6.5.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.