Offy is still making the 2 X 1V carb intakes and linkage sets the last time I checked. Any of the 2 x 1V Carb intakes is a big improvement over the stock 223 intake manifold giving you much better fuel distribution. Many of the old timers claimed that besides having more power they could also get better fuel economy too, they use to use the solid linkage so that both carbs worked together. I believe this claim has some merit just because of the Carb’s better placement, it would be interesting to see this tested out.
In my opinion the Clifford Ram Flow intakes with their much longer port runners were the best designed of any other intakes. They had them in a single 4V intake and 2 X 4V intakes. The duel is still being made last I checked in a complete kit buts quite pricey. I don’t know if the single 4 V that i had is still being made, Clifford back in the day also made some very nice long tube headers that I also had. Best of luck