Is my 350 on the outs?

[tommy3horse]

Hi folks, owned my truck for 2 years, rebuilt the turbo 350 when I got it and tuned the 350 and been having a blast. On Monday I ran a local errand. Along the way she started "missing", running like it had a vacuum leak. I checked the vac sources from the intake and replaced all hoses and nipples. Still running like crap.
Today I pulled the plugs and #7 was black and wet. Wires are newer and seem fine. Cap and rotor newer, HEI. I pulled off the radiator cap for grins and found a brown frothy mess.
Head gasket or intake gasket? BTW, I go thru a lot of oil, like a quart every200 miles or less, but no smoke...even at startup. Thinking it may be sucking oil thru the intake somewhere via a bad gasket? Help

Alum intake
76 block

Thanks,
Tom