losing oil pressure

I've got a '92 f150 and quite some time ago I noticed my oil pressure dropping while idling. I only have about 75k miles on this truck, but over the last 10 years it's been mostly stop and go driving around town. Anyway, now I'm noticing a "ticking" sound in the motor and I'm afraid the motor's going to blow. I have to try to get another year out of this truck if possible but because of the truck's condition in general, I don't want to put a lot of money into it (like a new engine). Does anybody have an opinion as to whether or not this engine may be repairable? or should I start looking for a used or rebuilt?. I started using heavier oil (10-40) plus 1 can of "restore" @ every oil change but I'm thinking about possibly using 15-40 the next time. I'm to the point now that I don't trust this truck for any lengthy travel. I sure would appreciate any ideas anyone might have as to what my options may be. Thanks in advance.

Just keep useing the heavyer oil, driver her, and don't take any long trips.

I would put a mechanical oil pressure gauge on it to verify the problem of actually losing oil pressure. Sometimes on the electric sending units get weak and dont read right in which case could just be the sending unit.