Using the info, you posted and what Melling says their MTF-4 cam specs are. Intake closes @.006-73- ABC. Dynamic compression isn't your problem. At sea level you are around 7.54-1 and at 5000 ft. around 6.5-1. At 7.54-1 you should be able to burn 91 oct. no problem. These numbers assume 100% volumetric efficiency, so you are actually less than that.

 

With those numbers it would seem that I'd need to get out and push my truck around town. No doubt some of my #s could be off but do remember that at 5300' dynamic was hovering just above 8:1.
Either way, to sum up;
If detonation is caused by a lean a/f ratio, solution would be to richen
if caused by advanced timing, then dial back
if high compression, then increase octane
if high cylinder temps, then cool it down
etc, etc
How would you know what specifically is causing ping since all sound the same? Do some of the solutions overlap? I definitely have a direction to go now but am not too keen on doing things that should theoretically correct issue but then in real world find myself 500mi from home halfway up a 10mi hill or in the middle of Nothing, AZ (yes there is such a place) with a blown engine. Also, what changes when pulling a load uphill? Truck ran fine empty. Point being, problem shows up at the worst possible time and not easy to just say let's try something else.
I am all in favor of overkill

 

With those numbers it would seem that I'd need to get out and push my truck around town.
Not really. You would be surprised at how low the dynamic compression was on some factory engines. For example, the 1973, 351C, Cobra Jet was only 5.94-1 and that was at sea level. Even in the heydays of the late 60's the dynamic compression on the high-performance engines was less than 8-1 and most were 7.5 ish. And that was when you could buy real gasoline instead of the camel **** we get now. Don't get me wrong I'm all for high static compression because it gives you way more camshaft choices.
If it were mine and I didn't want to spend a bunch of money. This is what I would try first.
Check the curve on the distributor and make sure it was not all in before 3500 rpm.
Put in the coldest plugs available.
This depends on which carburetor you have. If it has changeable air bleeds, change the high-speed air bleeds to a smaller size. Go down about .003 for a start. That will richen up the mixture at cruise. The air bleeds are the easiest way to make small changes in the fuel mixture since you don't have to take the carb apart to change them. Just don't drop one in the engine. If you do a long pair of tweezers will retrieve it.

 

I think the reason you may have got that dynamic compression number over 8-1 is you may have put in the timing at .050 lift. That will give you some numbers that are way too high.

 

Sounds like you need a good AFR gauge and O2 sensors to monitor what's happening at altitude and load variances. Makes it super easy (and kinda fun) tuning in your carb and distributor in addition to reading spark plugs.