Mild 318 pinging

Car and engine specs as follows. 1974 318 with Performer intake, 1406 carb, 204 214 278 288 .421 .444 112LS cam, factory 318 manifolds into duals. Short block and heads are 1974 stock original. Trans is a 904 with factory stall and rear has 2.76 gears. Idle timing is currently 11 initial at 750 with vacuum advance plugged. Its at 25 mechanical at 2000 rpm which is cruise rpm at 55 mph and 48 at 2000 with vacuum advance added. I know that my total max is 34 mechanical and 52 with vacuum advance added but I don't know what rpm as the tach I used to get these numbers only goes up to 2000. I also should add that I'm using ported vacuum advance.

My problem is pinging under load such as up hills when warmed up on hot days. This engine has always been prone to pinging since I have had it. Even when it was a bone stock 2 barrel with the untouched factory distributor in the 74 Valiant that it came from it would rattle if you put your foot in it.

If you took the time to read the book I wrote above, am I expecting too much to try to run this combo on 87 octane? Obviously, a 74 engine has fairly low compression, but I am running highway gears and I've had older guys tell me that the gas we use now wouldn't have been fit to kill weeds back in the day. My gut tells me that I should probably limit the max down to 28 - 30 and slow the curve as well. Basically try to pull 4 - 6 degrees out across the board while keeping the initial the same.

I'd appreciate any help and opinions you guys have even if you tell me I'm an idiot and have it all screwed up. With gas prices the way they are, I have no intentions of using even mid-grade gas so if I need to de-tune somewhat that's what I will do.