sudden valve clatter help please!

i was going down the interstate at around 75 when all of a sudden my truck started making what seemed to be alot of valve clattering noises and my speed dropped to around 60, i then pulled over and the noise continued at idle but not as severe, i killed the truck and popped my hood smoke was coming from the intake around the carb, and the truck is a 1990 b2200 by the way. i drove a little further to get off of interstate and somewhere my dad could safely come pull me. ive taken off the valve cover and nothing is visibly wrong to me but some of the rockers appeared to have a little more play between them and the valve than usual. im pretty much at a loss right now and my main idea is to just go get a entire head from a truck that i know is good and swap them out.
any help is appreciated greatly here guys!!

Have you checked to see if you have enough oil in the crankcase?

If it isn't even on the stick it's likely you are going to need more than a head.

there wasn't actually. what else will i likely need? rings and all that good stuff?

lessee. . .

crank

main bearings

rod bearings

oil pump

cam

probably a head, because the journals probably got destroyed

rings

maybe pistons

rocker shafts

maybe some other stuff

might as well throw a new clutch at it since you are going to have to take out the crank anyway. . .

timing belt

water pump

that ought to about do it.

maybe a thermostat.

new sparkplugs

boy, this sure is fun to spend your money