wont start

Ok for the last few days I have been trying to get my slant 6 started.

First problem
Bad gas. I removed the gas tank cleaned and refilled with good gas.
I do have gas flow into the carb.

Second problem
No spark. Found my issue and fixed it.

Third problem
Timing off, my uncle and I reset the timing by feeling the cylinder pressure. (well as close as you can.)

I changed the ignition coil

So we have spark, we have fuel, we believe the timing is near correct, but it still will not turn over, we get the occasional backfire.

We also have compression,
cylinder 1 105
cylinder 2 140
cylinder 3 120
cylinder 4 120
cylinder 5 120
cylinder 6 120

these were checked twice. so now I am at a loss, I am not sure why it still will not start. Any help would be awesome.

Thanks
Tony