What a douchebag, I say drive it to Carlisle regardless and deal with the problem when you get back (if you can't deal with it before). You might be able to take the door right off and take it to a body guy and have him pull the dent out. Deal with the imperfections when you get back. Sorry for...
Hi performance manifolds are $$$. I have a 440 in my 64 NY that I bought truck style shorty headers for. They took a little finessing to fit between the control arm on the passenger side, but I'm happy with them. They're cheap on eBay and you can scuff and shoot them to get them to last longer...
Here's a random one on eBay, but you can find them in other places without BRAKING (see what I did there?) the bank
NOS Mopar 1964-66 B+C-Body Brake Light Switch | eBay
Most likely the rubber o-ring in between those two parts. You shouldn't need to remove the gear box for that. Just unbolt those two bolts to remove that top part. Be aware though, once you put it back together, you'll need to SLIGHTLY adjust it left or right (depending) with soft taps before...
I have a 19 spline TC and you won't find any of those with different stall speeds. I had mine rebuilt to handle a higher stall (2800-ish). Not sure of the name of the company, but they came recommended to me by my transmission guy. You may want to consult a tranny shop and see what they say, or...