Oil back in the '50's didn't have much in the way of protective qualities.
Depending on how new your truck engine is, I'd recommend something along the lines of the miles it has on it.
Go to your local parts house and ask them what they have in the way of engine oil that would be best for the age of the engine.What oil type %26amp; weight is best to use?
Back in the mid to late sixties there were only four or five choices depending on the manufacturer. Straight 20 or 30 weights, 10W-30, 5W-20 AND 20W-40.
Most hot rodders (back then) preferred the straight weight oils as the multi-viscosity grades tended to disappear quite readily if the tiny but tough 283 motor was pushed hard. Everyone's favorite was straight 20 weight. Today it may be very difficult to find high detergent 20 weight.
Go to Joe Gibbs racing oil to see what they use to beak in their motors, qualify, rectrictor plate race and when the suffocating plates are not used. You'll be shocked!
Since the fifties motor oil has improved 10 fold. If your motor is freshly re-built to factory clearances I'd use 5W-30 during the cold winter months and 10W-30 in the summer. No heavier under no circumstances.
I've got a close buddy who builds asphalt and dirt modified racing engines. The asphalt cars of course run dry sump oiling systems in 358 ci. Chevrolet's. The oil of choice 10W-30 synthetic Valvoline Racing Oil. The dirt modifides are not allowed to run dry-sump oil systems. The oil of choice here is 20W-50. Remember however, these motors run an entire season with valve spring changes @ 7,800 rpm's.
For gosh sakes, never dump 10W-40 in any gasoline engine. The 10 weight spectrium of that oil dissapears within 1,000 miles. After that it becomes more like a 20w-40, much harder for the oil pump to pressureize critical engine parts on start-up. That's precicely where 80% of engine wear occurs. Heavy molasses motor oil milks horsepower from your motor as the oil pump is requred to work much harder and it does not cool the engine as well.
Hi, back in the old days oil was oil......its different today. Depending on how often you want to change your oil, or how many miles per year you will drive your old truck is how i would decide my needs. In my antique Dodge, with a 225 slant 6, i use Mobil 1 synthetic, 5w-30w.....i drive the car alot to shows and around town. Although the oil says its good for 15,000 miles, i tend to change it every 5-7000 miles depending on my finances, since the stuff is $6.25 a quart. Same thing with my new car. Mobil 1, 5w-30w, an 05 Dodge Neon. My old truck is a workhorse, i dont drive it much, a 74 GMC 3/4 ton with a 350. When i do use it, it gets used hard....lumberyard, 4,000 lbs. of rocks, towing, etc. I only drive it about 3,000 miles a year, it gets 10w-40w Castrol GTX. I change the oil about once a year, just because of condensation in the motor primarily. I have owned it 20 years, and its still runs well on the original motor, but is starting to smoke a bit when i start it up. Depending on the climate u live in lighter weight oil is used in winter, and heavier stuff in summer. Older vehicles like yours back in the day were generally run on 10w-30w in winter and 10w-40w in summer....at least in the Northeast. If you shop for oil nowadays, i think Mobil even offers a 0w-40w synthetic. Thats awesome!! Lightweight for starts on the coldest days, and heavyweight for summer driving. Back then some guys just used straight 30w ND,.....non detergent. Oil is oil to some people.......i take good care of my cars........but my boss, he's a bit different.........i work for a used car dealer....in 2 years i've seen him do ';one'; oil change....on his tow truck. Every car we got for sale, either traded or bought at the auction, he'll just top it off with the cheapest oil he can find....';Fred's discount store'; oil. The car may even have a serious oil leak....just ad more ';Fred's!'; And, wipe off the filter while your in there!! Thats his motto!! He dont care....old or new, they are all just pieces of crap to buy and sell.....we got 57 Apache, 67 Camaro, 67 El Camino, 38 Plymouth, and a variety of 1995 to 2007 stuff to. Good Luck!!
For that app, Valvoline Durablend 10w40. only one better is royal purple.