lctmjw

Personally, I would skip using RTV silicone in conjunction with the gasket, or at all in this application. The gasket by itself should be all you need, provided the metal surfaces are good and clean and it's screwed together snug enough.

Here's a photobucket link to the factory connector (I don't know yet how to post a picture directly): http://s36.photobucket.com/user/lctmjw12/media/Mobile%20Uploads/20160723_155830_zps13eisobr.jpg.html?sort=3&o=1

Jeez, that's like a quart every not quite two fillups.. Seems it would be smoking like a chimney burning that much oil.

Also, make sure the system is free of air. I like to elevate a vehicle till the rad is the absolute highest point, fill/top off with the engine running, rad cap off, for 20 minutes or so. Then cap it, drop it, and roadtest. Not really a problem with these trucks since the radiator sits up tall, but my Supra was a real pain. Rad sat low and the high point of the cooling system was the turbocharger, required a lot of front end lift and patience.

Once you're sure the cooling system is leak-free, there's not too much else to check that hasn't already been covered. Water pump function, rad cap holds pressure, thermostat, hoses in good shape/not collapsed, heater core function, ignition timing, fan and clutch operation. I mention clogged cat because it often gets overlooked, but it's a longshot. Also, how much oil is getting burned? Rings often fail from tension loss after an overheat condition, may explain oil consumption.

Shit, I wasn't reading carefully enough, thought you were the op. Checking cat without removal? Likely no way to know for sure without removing it, but shake the exhaust side to side if you can. If there's rattling in there, the material inside has collapsed some and can jam the exhaust. You can gently tap the cat itself too listening for rattling noise, but do so carefully.

Going back to your first post, headers are/were glowing red hot? Good advice already posted about checking spark and timing, but if your truck has a catalytic converter still, make sure it isn't clogged up. A clogged cat could explain the symptoms you've posted thus far.

The cooling system has to be free of leaks, even a small one can cause an overheat condition. Thr cooling system is pressurized and has to remain so to circulate coolant properly. Being under pressure also increases the boiling point of water. Mend up your leak before troubleshooting further.

In addition to the broken green crayon issue, I also had an issue recently with the drivers side caliper sticking. I noticed when I pulled into the garage, I could smell a faint burning smell. The rotor was way hot, so I disassembled the caliper and sure enough the piston was stuck. Oddly, the pins were in great shape, well-lubed and slid freely. Popped out the piston, cleaned a little scale/rust, put in new seals and put it all back together (and these calipers are only 20k miles old, genuine Nissan NOS) and bled. All was well for a week or so, and it started to pull left full time. The real problem was an internally collapsed brake hose (the rubber line to the caliper). It wasn't allowing for a full return of the fluid after the pedal's release, causing the piston to "stick". The hose looked fine on the outside, you can't always see a collapsed hose.

I had a similar issue with my 720 a couple years ago. After a 900 mile trip, I noticed the brake lights were stuck on. I found what looked like pieces of broken green crayon on the drivers side floormat, peeked behind the dash at the pedal assembly and realized that the crumbled pieces were part of the stop light switch "cap", if that makes sense, it's the piece from the pedal return action that contacts the switch plunger and turns the stop lamps off. Hard to explain without pictures, but was easy to fix with a small nut/bolt combo until I got the right parts to fix it.