I didn't see where you said the hood to core support seal is on the hood. If it isn't that can cause issues, as it allows air to come in between the hood and core support that would normally be coming through the grill.
But if you aren't going over 200* and you aren't experiencing boil over I...
Well, with 4:10's and cruising at 60mph your turning what, 33 to 3500 RPM's?
A 10* rise in temp doesn't seem out of the realm of possibility with the engine working a little harder. Do you have the hood to core support seal in place?
That mating surface in the second pis looks pretty waffled to me. Take a piece of wet or dry sand paper, lay it on a flat surface, and sand that thing flat, by gripping the neck and moving it around on the sand paper.
The stat fits like most I have ever seen.
Just because the stat is new, doesn't mean it's good. Pull it and put it in a pan of water, use a candy thermometer to see when it is opening, IF it is opening.
Don't mean it's good. I would question it.
Check the water temp in the rad once the engine is warmed up.
Did you check the stat to make sure it's opening at 180*?
I did think about that, and I may change it, just need a longer hose. It has a barbed fitting so a small clamp and I know it wouldn't pop off. Then just leave the petcock open.
All you have to do is attach a hose inside to the inlet tube, that's what I did with mine, it works like a champ. Mine has a petcock on the bottom to drain it, now I don't have to use it.
But you're right, it is only a puke tank.
Why not remove the sensor that is in there, and replace it with the new one?
Just make sure the gauge and sensor are matched to each other. I bought a complete kit, gauge, sensor mount etc.
Thanks, I am planning on doing the ammeter bypass, so at that point I assume I can upgrade the alternator.
Accessories? Lol, the only thing I have is lights and wipers. :D