Which grade oil should I use for my motor?

[Isaiah92260]

Hello everyone, if you havnt seen my other two threads, I am fairly new to Classic Chevy's. My question I want to ask is, what grade of oil should I use for my high milage motor? I have a 1967 Straight 6 motor. My odometer says 36,000, and for a 63' C10, I'm gonna assume that means it's anywhere from 136,000-236,000 miles. The motor isn't obviously original to the car, so I can't really say how many miles there are on if, but I'm guessing it has anywhere from 90,00-135,000 miles on it already. I don't have the money to rebuild my motor, so I'm wondering what kind of oil should I use that will make it last longer and reduce wear, I live in Palm springs. So it gets 100+ out here during the summer. I only drive the truck 20 minuets a day to work and home, but I do plan on drivin it more on te weekends.