FELLAS, its not a vacume pump ! it pressureizes the front & rear axle,trans,t-case,master cylinder and distributor. this is all part of the waterproofing for fording. it also makes the wipers work. if it made vacume it would suck water in these components but if there pressureized it will prevent water from entering. i dont mean to be rude but it hurts to see such fine trucks jack legged. this truck is better than any 70k$ truck made today and will last you your lifetime if taken care of. to be honest the engine you have is probably hurt so heres my suggestions.
install a bone stock sbc......
change out the t-case to a np202 or np205
replace the master cylinder with a "truck " split master cylinder
move battery under hood
change over to 12 volt
install a fsj bench seat
go 100% thru the brakes
clean,inspect all wheel bearings and relube them with hi-quality grease
change all fluids IE: TRANS,& DIFFS
make sure all grease fittings take grease and lube them every 2k miles (I highly recomend synthetic grease -amsoil)
change truck to power steering (you,ll be glad you did)
this will keep you busy for a while........