And I would suggest installing a new double roller timing set as well. No better time than now. About $50.

 

Found the leak finally but have no clue about the gauge. Truck no longer overheats. It was a PSI leak that wasn't showing until i pumped the system up over 30psi [way further than normal, but it finally flashed off and I could see it.] around the heater core inlet hose on the block side.

My gauge is still funky though. Always 5-10 degrees right of half way. I was crawling uphill on the mountain in 4 low with the A/C on for hours in 98 degree heat few days back, never got hotter than the normal few degree rise. So good enough for me. At this point I think its just the gauge wiring or something and im not going to mess with it.