According to the Assembly Manual, it appears GM added two pellets of their sealing compound to the radiator of all Camaros.

When it’s time to drain everything, remember to remove both water bolts from the lower heads cause there’s a sh!t load of coolant in the block.

I got one of the 1/4" pipe plugs out on the starter side to drain the water from above the pan rail. Looks like I will need to remove some of the eng mount on the driver's side to pull that plug. It has the later design safety bracket in case of eng lift. that's in the way.

I checked all the ground to make sure they were actually grounds. I did notice where I painted the starter assm & then scraped some of the paint off where it bolts to the block, it did leave a slight step from the paint maybe not allowing it to sit flat against the block. I hit both surfaces with a Roloc just to make sure I had a good ground at that point....thanks, Joe

Tap water is typically loaded with dissolved solids that will boost conductivity. As a result, you can create a galvanic corrosion cell within the cooling system.

The stainless freeze plugs referenced in here (US Tool) have been great for us. Stainless has a lot more strength and is stiffer than brass so they tend to stay in place better as well.

I'm still getting alot of garbage when I drain the block so I have a question.

Could I do any damage by pulling the thermostat, blocking off the water pump inlet & heater hose connections & filling the block with clean evap-o-rust?

Thanks again, Joe

Evaporust actually makes a cooling system cleaner:
https://www.evapo-rust.com/thermocure/

Not sure the difference between thermocure and the regular Evaporust product, but I don't see the regular product causing an issue. Guessing the thermocure has some changes so it can be used as temporary engine coolant.

Oxalic acid https://en.wikipedia.org/wiki/Oxalic_acid was the main ingredient in the old chemical flush that came in a two part can from your local auto parts store or dealership parts department, that came with a neutralizer in the lower half of the can.

Oxalic acid's main applications include cleaning or bleaching, especially for the removal of rust (iron complexing agent). Its utility in rust removal agents is due to its forming a stable, water-soluble salt with ferric iron, ferrioxalate ion.

Since my last post I've been rinsing out the inside of the block. Rinsing is becoming cleaner each time. I've rinsed out the heater core & the radiator. Took the top & bottom hoses off & cleaned them. The spring in the lower hose was rusty but still usable. I took out the thermostat, blocked the heater hose connections on the engine & blocked the water pump where the bottom radiator hose goes. Tuesday about noon I filled the block with Evaporust. It's been sitting since. The positive side is I don't see anything dripping. Later today I will drain it off, strain it & possible return it to the block. I'll see what it looks like after draining.....Joe

Drained & strained the evaporust & started rinsing the block....again. Decided to connect the radiator & heater core. Leaving the thermostat out & refilling the entire system with evaporust. Installed the starter & now running the engine until it reaches 160 degrees. The people at Evaporust says heat & fluid movement will help desolve the rust. I will continue doing this through the weekend & drain all the evaporust. I will then start flushing the system with clean conditioned water from the house. This is really bugging me. The car sat for 15 years. Maybe I should've just tore down the block for a complete cleaning.

On positive note, I fixed the tranmission leak....Joe

Latest update. Did all the rinsing & drainng of everything. Evaporust foams up when run in the engine. Took alot of flushing. Mixed 50/50 deizonied water with green coolant. Ran it & tested the new mix at 100 degrees. -43, 1,200 plus on the nitrite, 7.5 on the ph. Took it for a 20 mile drive today. Did a retest at 160 degrees & got the same results. I bought coolant test strips & I'm going to test it every time I come back from a drive till I think the problem is gone. I did fix a trans leak as I indicated before. Also fixed an engine oil leak which was alot less fun. I had to pull the trans & reseal oil galley plugs....Joe