1987 F350 clutch question
 

hey fellas im new to this forum but not the f series pick up.
but what i am new to is clutches. i picked up a 1987 f350 4speed with a 460 engine, i picked it up solely because it came with a plow.

the other day i was leaving work and i went to take off and the rpms went real high like the clutch was not grabbing, then it did and sounded like 1st and 2nd were chattering, after that 1st and 2nd sounded fine, but then i noticed when i hit a stretch of road that is 50mph i had it in 4th gear and the rpms were real high and i wasnt going that fast. and i could smell the clutch burning.

so i assume the clutch is going, but i dont know what size i am getting, it has the 7.5 460 engine with the 4 speed,really low geared like driving a tractor trailer truck, i mean i am in 4th gear in a matter of seconds. anyone have an idea what size clutch i should get, and how hard is the process of changing in this truck, thanks guys

Well went out to today to start it up, push the clutch in starts up.. Put it in any gear and nothing, can let the clutch out in any gear including reverse, and it just revs no movement or try to move, i do hear slight grinding likes its just touching but that is it, should i assume the clutch is completely gone?