FWIW, Don't use the distributor from the 305 in the 350. You can wire up a lock up converter switch via several means and a few companies sell a kit for it so you can retain the converter lock up on your th350c. Pretty common stuff, just do a little searching.
Start by searching something like "lock up converter switch th350c" in our search bar or Google. You'll find a ton of info and it keeps our regulars from having to feel like broken records.
As far as swapping in 700R4, the extra gear is nice, but without the right combo you can render your first gear useless. The 2004R has a way better gear spread for a performance car and also comes with overdrive.