LA 318 compression numbers

Do you have access to a leakdown test kit? That could tell you how well the rings and valves seal and if it will respond well to a tune up.

I'll bet you that part of your low compression problem is coming from a worn timing chain.

When timing chains stretch, it retards the valve timing against the crank/ rod/ piston.

Ultimately, it's negative affect on cylinder pressure is that the intake valve closes late, after the piston is already on it's upstroke, so you lose compression for some of the total stroke. This also diminishes flow, coming from the intake, as the piston counteracts it's draw from the intake runners. Even a good double roller on a stock cam at 0° can be improved with a timing chain/ gear set that allows a little more advance on the valve timing, so the intake valve closes even sooner.

To check timing chain stretch, put the engine at TDC going clockwise and have your friend eyeball the distributor rotor with the cap off. Move the crank counterclockwise until you see the distributor budge and stop. Give about 1° or so margin of error and that is the amount of retardation the valvetrain has. 3° advanced from 0° stock makes a big improvement, so if you are seeing more than that in retardation, it will respond well to a good double roller timing chain set with multiple keyways to set more advance. It also helps dramatically with consistency in ignition timing.

Static compression ratio numbers advertised were down around 8.5:1, which were optimistic. I'd imagine it's somewhere in a 7.8:1 range, stock.

Hope this helps.