I'd guess the pins are glued in. The emblems are probably pot metal and that might make soldering, or brazing difficult. I'd try a good epoxy. On the 500 emblems a satin black paint should work. SEM makes a trim black paint that should look good. Good catylized paint and satin clear might provide longer life, but only if you have the equipment.

Excellent work! Nice to see a plan come together.

This sounds like a cool project. I've never played with boost, but I'd think that in a low boost application that stock manifolds would be fine, even though they tend to be poor performers on the exhaust side. The key factor may be the best packaging. Which puts the turbos in the best locations? Manifolds, or headers?

Yeah, that looks like something that is not meant to come apart. Maybe a good time for a disc brake conversion.

It always seems that a better deal will surface after you buy something, no matter how long and hard you look. Just think about how much more fun you had playing with all that metal work on the car you bought. You would have missed all that if you found a better car to start. You won in the end.