what plugs are in there? they may be too cold, and keeping too much heat in the electrode causing it to pre-ignite.

also, if the oil was burning for some time there may be very bad carbon deposits that are getting heated to an incandescent temps and igniting the incoming fuel/air charge.

i have not needed to myself, but know of many people who have used sea-foam as well as a GM labeled de-carbonization product to clean up the combustion chambers, ports, and valves. i have heard nothing but praise....its cheap and worth a shot. from what i remember you turn up the idle to about 1500 and take the vac hose off the booster and put it in the bottle to let it suck out all the chemical. something like that.

choke open throttle open for compression test. its been a while since i compression tested one of those, but i really think 175+ is what you want to see. maybe 150 for an OLD engine. of course a big cam with excessive valve overlap can make for lower readings.

within the next few days we should have my brothers tranny back together and we will be able to start the engine, ill toss the tester on it and see what his fresh rebuilt 351 is throwing for numbers.