Glad to see another build thread being started. Keep it detailed and up to date with the potential to have it added to the lengthy FAQ section.
Welded diff won't be a biggie in the rain, ran a spool for years then a locker. Just know it eats tires faster but w boost its gonna happen
I wouldn't worry too much on jet/ horsepower etc bc each build is unique. If going holley 2300 I'd suggest a 350 so that it's still decent when not in boost. You can always upgrade later to a 500 if you want, like when you go bigger turbo. The tdo4 will prolly be small but upside is you'll build boost at about 1500 rpm and choked out by 4k. Give or take a bit since there's a few diff tdo4s.
Start simple and work up. Shaker223 ran over 20# on stock motor w only 340 valve springs, so it can be done w stock but the key is to have a good tune as you said. Start at say 5# and learn all you can like how much the jet needs to change or the pvcr need to be enlarged to achieve a desired outcome, then go for 10 and so on. Also if you work in stages you can drive more and be down less, like the super six and holley swap, once it's tuned via wbo2 then add electric fuel pump and regulator etc etc, this way you build up to it instead of a coughing up all the money at once and being down longer.
So longer story short, if its running now, just go w what you have and build up, make notes here as you make changes and we will help as best we can, there's more to see this that have volumes of knowledge over me too. I'm sure they will input here too.
Keep on wrenching and get some before pics up
Ps, mr gasket 1937 to get the holley onto a super 6 intake
Pohlman