If for nothing else everyone should have a small oxy-acet kit to use with a rosebud to heat things up. I have brazed cast iron using brass with oxy-acet and have gotten better results than trying to weld it.
Add a cutting torch to the kit and it provides a lot of time saving in cutting metal and/or cutting old brackets off, stuff like that. Seems you have some time on oxy-acet, so not sure why you're so dismissive about it.
I agree with you TradToolWorks, that an OA setup is a necessary tool for working on our old trucks. I have gas welded allot in my career as a machinist, so I’m not being dismissive, but more of a realists as to the capabilities of a new gas welder. Working on a hard to find rear door on a burb (or panel), I wouldn’t want to tell a fellow ‘bolter to gas weld it only to find out the process made it worse. As I said, I don’t know the OP’s capabilities. If he spends enough time to learn the process, then I say go for it.
My recommendation to braze was due to the fact that the OP is fairly new to welding, and it does work really well. Back in the early 70’s, replacement panels were flanged, pop riveted on, then brazed in most “production” shops. Note that I said “production” shops, meaning shops that did mostly insurance repairs, as that was where your bread and butter was. That process helped limit the heat introduced into the panel to minimize warpage and was an accepted practice in the industry. Most shops back then only used OA setups. TIG and MIG were in their infancies and expensive.
HOWEVER, having said all that, today, TIG would be the best choice. I don’t own a TIG setup so I would MIG it.