'68 Barracuda Formula S Fastback Restoration Background

340S Fastback,
I was considering the conversion to a Tremec trans for a long time but couldn't justify the floor pan mods and trans crossmember cutting on a car that essentially had no damage or rust in that area. So some recommended a GearVender, but I need to see exactly how that installs before considering that option. But having an overdrive is tempting. I have the old fashion OD. Swapping gears in the 8 3/4. I have 3:55 stock and a set of 2:94's with SureGrip for highway. Not ideal, but it works.