In re selling, I think I will share my experience:
My truck spent one summer (my busy season when I most need it) constantly letting me down: A huge exhaust leak that I battled for ever, Overheating issues that (I think) ended up killing the ignitor, oil loss that would put the Exxon Valdeez to shame, and constant battles with the atrocious neglect and shoddy maintainance by previous owners. After the ignitor went out I decided to sell it.
Long story short: It turned out that it was less trouble and expense for me to stick with a vehicle that had known problems, even several major ones, than to take on a new vehicle with a whole new batch of unknown problems. If I were you I'd let the truck be for a couple weeks while puzzling on it. A solution might just come to you at 3 AM one day.
Speaking of which, are the mating surfaces flat? Is the plate bent? What happens if you turn the plate front-to-back and try again? Does the leak go away? Does it move? Is there a blockage in the coolant passage that puts undue pressure on your sealing job? Can you drill and tap some extra bolt holes to squish the plate against the intake where it's leaking?
Can you go back to the old intake manifold? I know the two-piece adapter is not well liked, but could you weld the two pieces together? Do you have any machinist buddies who could make a one-piece adapter for a reasonable cost? Do you want to buy a milling machine and make one yourself? (Okay, buying a $1200 milling machine to fix a coolant leak is overkill, but at least you have the milling machine afterwards!)
These are just a few ideas and suggestions. At the risk of sounding like Gnarly, they may be worthless
Hey Lewis, thank you for your thoughts on the matter of selling my rigs. I've come to the conclusion at the moment that I will just hang on to them. You are right, any other truck I get will be it's own can of worms. Potentially greater issues, potentially none.
Makes sense to stick with what I know!
I do have my original intake manifold with the two piece adapter. If it comes to it, I will just install it and sell (Or fix) my Offenhauser.
Welding the water plate to the intake makes sense, I would have to wrangle with heat distortion/warpage. The plate is billet aluminum, and the intake is cast aluminum. TIG Bronze brazing might be a better idea.
The plate can only be installed one way unfortunately. I do believe the plate is flat, but I could be wrong. If I have to remove it to drill and tap new holes, might as well permanently weld it on. Thanks again!