The Super Six was only offered for 4-5 years, and not in California. At this point in time finding a complete setup will be near impossible, and likely very expensive if you do. In any event, there are actually better and more affordable parts on the market now.

My advice to you is as follows:

(1) Don't worry about a Super Six. If you are just going to use your truck as a cruiser then you really don't need to go through the expense and hassle of a two barrel carb swap.

(2) Get what you have running well first. You are already having difficulty getting your one barrel system up and running and getting your timing dialed in. The last thing you want to do is start changing variables like the intake and carb. Take it one step and one modification at a time. Get what you have running well and THEN worry about upgrading the carb.

(3) If you do go for a two barrel setup, don't try and find a complete factory setup- be willing to mix and match aftermarket and factory pieces. A factory Super Six package included a two barrel carb (Carter BBD or Holley 2280 designed specifically for a slant six), a two barrel kick down linkage (including the kick down lever on the transmission) if it was an automatic transmission vehicle, a two barrel air cleaner, and a 2 1/4 inch exhaust line. The air cleaner from most any two barrel 318 powered vehicle will work. You will need one with the clearance dent for the AC compressor. The two barrel intake can be purchased or fabricated, and there are aftermarket options. If you have an auto trans you can use a cable style kick down which is much cheaper and easier to find than a factory two barrel kick down. Correct BBDs and 2280s are hard to find in good condition. Parts store remans are a crap shoot. Try and find a NOS slant six specific 2280 or BBD or adapt a new Holley carb to the engine.