I've run Chevron Delo400 15-40 in mine quite a bit, but I don't think there is really a need for it. 10-30 is good for most climates. If you find that it smokes, go up a grade next oil change and see what it does for you. My 79 really liked to have 15-40 or it would smoke on startup, but my 77 (with more and harder miles on the motor) doesn't smoke or use much on 10-30.
If you want to spend a bunch of money on oil, Mobil1 10-30 fully synthetic is some good stuff. You have to watch putting synthetic in an older motor though as it can sometimes cause old seals to start leaking. It cleans the gunk out of the motor a little better, and in the process can open up old brittle seals.
_________________
95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)
MEPR: Man, my 4x4 makes all other LUVs look good
