So first, I would say with a piston .020 or so down the hole, and the heads you run, assuming an 8554 head gasket, you just have low static compression for the cam. Depending on how much your heads and block were cut, and using the blue gasket, you could be at 9:1 for a cam that would prefer 9.75-10:1 in a 390, add the 60 degrees of overlap and you lose bottom end
Low compression and overlap will also show itself as low vacuum as well, even worse if timing is late.
Those cylinders don't look bad to me, it will be interesting to see what the heads do, but I don't expect much wrong.
So you could just advance the heck out of the cam, but if you advance that cam, assuming you advanced it to 102, you'd gain some torque, however that piston likely doesn't have a lot of room for the intake valve. You would have to measure clearances, both lift and radial (especially radial)
I see three courses of action after you determine if the valve job is good, and they apply even if you find something in the heads.
1 - Put it back together, crank up the initial to about 16, recurve the distributor like RJP said. "Tune it option"
2 - Put it back together, checking valve clearance and advance the cam 2-4 degrees and recurve the distributor like RJP said. "Drive up low end power and tune it option"
3 - Rebuild it to modern specs, (leave the cam at 106, .045 or so quench, lots of room for valves, forged pistons, modern ring set, cc the heads, deck it to make sure it's straight, and get at least a 1/2 point of compression more up to about 9.9:1, and then recurve to something like 12-14 initial, 36 total all in by 2800. "The best option if budget allows"
The thing I'd like to point out though, is the heat is likely only related to performance if your ignition timing is retarded. If it is not late, then it is a likely separate issue, and likely more related to the fan you run.
Again though, I'd really look close at ignition timing, we know you are low compression for the cam, so it won't ever be low end torquer without changes, but the combination of heat and low vacuum indicate ignition timing issue.
If that is not the case, then I would add compression or advance the cam, and then go find why it runs hot