there's nothing you can do to a 'standard' 4 speed that will change the fact that the highest gear is 1:1, you cannot convert it to an overdrive .... depending on the year, you may be able to just replace the rear gears, keeping the closed drive
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
