Well, THANKS for all of you chiming in..
I'm preplexed, brief history PRECEEDING , I purchased the truck in Sacramento in Feb 12 , 2005, flew down & Deove the 1200 miles trouble free, MT, Shasta Pass, snow & cold rain. When i returned home, i took the trk to this shop, & basically said, " this is my first chevy, treat it like your grandmother's & tell me what i need to fix? "
few things engine wise,
1. One missing freeze plug,- but no coolant overheating ,,,fixed.
2. radiator leak,- I had the radiator rebuilt due to leaking rebuilt & If memnory serves me 7-8 lb cap.,
3. Chrome thermostat housing blow thru, / no thermostat - replaced with cast iron, added 180. degree thermostat .
4. added automatic choke.
5. truck has ram horn exhaust manifolds. Since posing received a message that they are installing a " starter blanket or wrap.

35Window:
1. no, not a vented cap,
2. no visual sign of any frost, or extreme colld temp.
3. never checked the gas tank for sucking sound..

My secondary reason for ' being in the shop' is to make sure everything underneath was tightened down from the paint shop ( they forgot to tighten the LF wheel, ,,,I got about 3 blocks before I had to stop, i thighted the remaining 5 lugs & promptly headed to Les Schabb to have the wheel checked & replace lug.

Since the hood was off for the 2/1/2 mo. I thought maybe all the accumulated sanding dust, could be a problem & to clean out / check the fuel pump.
big thanks for all of you chiming in...
if I could send you a poster i would.
jim