1991 Ford Ranger engine noise

I was driving truck when I down shifted to second my engine started too make a this noise
it is internal noise clicking noise that picks up with the rpm and drops to idle when the clutch is in
the clicking stay with the engine it sounds like a rocker spring broke or came off
but I was also told that it can make that noise if the oil pump goes bad
but my oil preussure gauge is either broke or there in none oil pressure can some one tell my if I can still drive my truck like this or if the engine is shot
if u have any info on this please help