Yes, I closed the rear coolant passages. They serve no purpose and will never ever be used on this truck. The right rear was leaking after our trip to see the solar eclipse. The head gasket was also leaking oil into the coolant system and there was some cylinder blow going into the coolant system. All this happened when the water pump failed and we had a boil over and over heat on the day we left for our trip to Texas which due to weather, turned into Arkansas, to see the eclipse. As the trip progressed over the next couple months, so did all the leaking. So I'm doing what I can to try and prevent head gasket failure from happening again. The Cometic gaskets are supposed to seal really well and handle a 1000 plus horse power. Welding shut the rear coolant passages prevents two leak points from happening again.
I'm hoping the headers, exhaust porting, and port matching the exhaust ports to the headers, and the Y-Pipe to straighten out the exhaust and remove two choke points in the exhaust will help increase horse power. The cold air intake I fashioned may or may not help but the cold air inlet is now 3-1/2" where it was 2-1/2" before. That's got to be good for something. The rear of the head coolant adaptors are supposed to promote more even cooling in the heads and eliminate the hot spots at cylinders #4 and #8. Also installing a high volume oil pump, new timing chains, guides, and tensioners. That brings you up to date on all the projects done to hopefully improve the engine. There are about 5 or so videos I didn't post here that will show the other work if you're interested. Take care.
