Dealing with roof and A-pillar rust through

[Cdorp]

Looking for some skilled input for someone(me) who has lots of tool and woodworking experience, but not a lot of metal work. I am working on a cab for my dad's 69 C10 LWB. Looking for this to be a driver, not a show truck.

The original cab is rough in lots of places. I picked up a titled cab with very little repairs needed in the floor and firewall. But when I pulled the glass and started poking around, I found rust from corner to corner of the inner header. There is one hole in each of the A-pillar and roof on the driver side. Also holes in the top of the passenger door opening.
The seller made it a package deal with a non-titled cab as well. I haven't removed the glass and poked around on this one yet, but there are no signs of rust rot in the roof. I'm considering a top swap, but hate to cut up a decent cab (non-titled) that I intended to sell.

What advise and direction would you give with these options:
1. Buy the inner header patch panel, and then cut and replace other holes with patches. What's the best way to deal with the A-piller and roof holes? Would removing the roof panel be a good idea for treating the hidden rust?

2. Cut patch panels out of the non-titled cab.

3. Doing a top swap. Makes me nervous, but think I can make it happen with a couple buddies and scouring the helpful posts here.

Also, are there any good threads for dealing with the seams around the windows? I've seen some pics of trucks where those seams have been smoothed out. Curious how that was done--weld, fiberglass, combo of both, etc.

Thanks for your helpful suggestions.