Just got my first slant six

Your first step is to get the three books described in this thread.

Your compression sounds very low—assuming the test was done correctly, that is with all six spark plugs removed, a fully-charged battery, the engine warmed up to operating temperature, and the choke and throttle wide open.

In any event, Tune-up parts and technique suggestions in this thread. The engine requires periodic valve adjustment. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.