Buddy did same swap, callbacks vanished too.

That sinking feeling when you realize your hands lied to you for years is the worst. Feeler gauges are one of those cheap things that make you wonder why you didn't grab them sooner.

Do you have anyone pumping vinegar down there, or just trying to muscle it? Because if the pin is frozen from rust and scale, no wrench is going to win that fight, you are just stripping corners and ruining the tide. The trick that saves me is soaking it first, the same way you would on deck. Drop a funnel or a piece of hose over the shackle and feed it straight vinegar or a cheap rust spray, then go do something else for a bit and come back. That soak does more than any cheater bar ever will.