Freak,
You have the BEST carb now. I would NOT use a street demon. I have installed two of them. They are cheaply made, nothing like the Carter quality. One worked ok [ on a Chebby ], the other on a 400 Pontiac ALWAYS had a flat spot that no amount of tuning could fix. The owner actually phoned Holley tech from Australia for help. About as useful as a sun roof on a submarine...
After reading through his computer scroll, the tech had no more ideas...or help. Pontiac owner ended up refitting his QJ, which is still there many years later.
I also recall that to change met rods on the SD risked dropping a circlip into the throttle bore...Not a good design.
Back to the TQ. Just get a gasket/overhaul kit. The pods under the pri main jets might be leaking. Very easy to fix, have done heaps of them. Scrape away the old epoxy & dig a slight channel [ with tip of a knife ] into the joint; re-epoxy with fuel proof epoxy.
You can re-use your centre section & airhorn, just replace the worn base. There is no jetting/metering in the base except for some models that have bypass air holes in the primaries. This is also not a problem. If there are holes in your old base & they are bigger, simply enlarge the holes in the new base.
If the new base has bigger holes, do this: enlarge the existing holes to the next drill size, but do not drill right through. Measure the hole depth; cut off the drill bit shank a little shorter & drop this in the hole. Peen the alum over so that is locked in place. Drill new, smaller holes, next to the old holes if bypass air is reqd. Another thing you can is drill bypass holes in the secondary blades if more convenient.
