Welcome to the forum. Well, for your dipstick and throttle cable I would suggest Lokar. They make a variety of both and are very good quality. Yes, you will want your primaries opened wide to allow the secondaries to come in. Even with the new cable you might have to play games with the positioning of the cable end to effect enough travel to open it up all the way. Kind of a two man job., one watching the carb butterflies and one stepping on the pedal.
Buddy of mine built a 49 Lincoln for his Brother, also had a sbc in it. Cool cars, sort of 50 Merc-ish looking, but different in a good way. As for parts, you are on your own on those. I know of no or few aftermarket parts for these, but you might try joining a Lincoln owners forum or club and also scouring Ebay.

Good luck.

Don