I have a 1978, with the original stock 350 4 barrel. On page 1-13 of the Owners Manual it says:

"Your engine is desined to run on unleaded gasoline with an octane rating of approximately 91"

In the three years and about 3000 miles I have had this vehicle I have used regular 87 octane gas with no problems I am aware of.
What gas do you guys in stock engines??

Thanks and have a great weekend

As long as you don't have PRE-IGNITION issues, (properly tuned Motor) you are fine with the 87.
Higher Compression Engines need the 91. And in your case, the 91 would be an unnecessary expense.

As previously said I would say you do not need it get higher octane. If your car start to get out of wack and you can see a difference in it then go to 91. Another option is you could still put in 87 octane gas and then you could buy a octane booster. It will boost the octane you stick into the car and you do not have to pay 40 cents more for the higher gas.

Don't forget the method of figuring octane changed in the last 20 some years. If it's running fine on 87, use 87.

At least you looked in your owner's manual:smileyb: Most folks never look at those even after owning the car for years:smileyb: