'68 Galaxie 302 poor running...

What a vacation... Cars will always choose the worst possible time to break down... 300 miles from home! I got back from my two week vacation to Maine
last weekend. I'll try to give the short version of the story.
My car gave me trouble starting when I got about halfway there. It was running poorly and backfiring through the intake and exhaust, and had no power. I filed and re-gapped the points and it ran much better, got me up to ME. I had to re-agap the points a couple times as they kept getting out of whack. Before I left I had replaced the spark plugs, when I got up there I replaced the wires, cap, rotor, points and condenser. This greatly improved the cars performance, but it still ran poorly, thoguh much smoother. I backed off the vacuum advance by tightening it two turns and that got rid of the pinging that had developed since I left NJ if I used anything but 93 octane. Now back to 89 and running better.
When hauling ass up hills at WOT or near it there are occasional wisps of light grayish smoke from the exhaust. When moving at a higher speed and letting go of the gas pedal there is light backfiring thorugh the exhaust. At one spot in the throttle when under heavy load (climbing hills, etc.) I will hear a light backfiring, can't tell if it's through the exhaust or intake. Exhaust has a couple holes, which may be contributing by allowing oxygen in to any unburnt fuel while it's still hot.
Did a compression test tonight. Engine was warm and cranked 4 times for each cylinder, also recorded is plug color. Plugs have ~ 1,500 miles on them.
Cyl | dry | wet | plug color 1 | 155 | 185 | white/light brown 2 | 150 | 165 | white/light brown 3 | 155 | 180 | white 4 | 150 | 180 | white 5 | 120 | 135 | white 6 | 60 | 70 | dark brown 7 | 155 | 170 | white 8 | 155 | 180 | white
This indicates to me a blown head gasket, from low compression on #5 and #5 (next to each other), which from the wet test does not appear to be from worn rings. This hypothesis is supported by the white plug color on #5, which was likely steam cleaned by a small coolant leak into that cylinder. Plug wire #1 was loose and not clipped on. This likely resulted in a misfire which would partially explain some of teh backfiring and rough running, as well as the light brown color when most of the otehr healthy cylinder plugs were still white and looked practically new. Also, a coolant leak into cylinder #5 would easily account for the light grayish smoke when reaching WOT under load. I also noticed the coolant level in my recovery tank (tube from radiator ran into non-functional windshield washer reservoir) was a bit low, maybe 1/3 full. It was 3/4 or more full when I left for ME.
My other theory, which is more wishful thinking than anything is that the valves are adjusted too tight on cylinders #5 and #6. That would result in lower compression and could very well cause backfiring. This is rather unlikely though, and the evidence points to a head gasket, warped head, or some other problem of that nature.
What do you guys think the problem is? Also, is my thought process logical? Thanks for any suggestions or insights into my problem.
Cory
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[snip]

Do a cylinder leakdown test.
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You will obviously have to take it apart anyway to fix whatever it is so after you rip it apart come back and tell use what you found. I would expect bad values.
Cory Dunkle wrote:

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