Slant 6 troubleshoot help!

adjust your valves, .012/.022 a little on the loose side of .010/.020. Also check your intake gasket. Where is that large vacuum line going? Plug it for testing purposes. Its PCV, not needed for idle testing. I bet you got low vacuum on a guage at idle, massive vacuum leak.
Had time in between work and class to plug that tube on the pcv end and it ended up idling a helluva lot better and stayed running. ordered the pcv and should be here hopefully by the weekend. Sadly the mechanics in my town are quite clueless... I’ve replaced part after part they “thought” were causing the problem but they never once brought up a vacuum leak. Sucks living in a fairly isolated area with no good mechanics. I thank everyone who responded. once I install need pcv, I’ll update again.