If it's a 1977, you're lucky to have a Del - most early ones came with an Encarwi. To put a kit on an A3 though, you need a different wrist pin bushing on your crank. Do a search for A3 kit and you'll get some good explanations.
Even if you do kit it (you would probably use an A35 kit) there aren't many good options for the carb and intake. Unless you make an intake, you either get the SHA intake from treats (I think it's 13 mm) or a jcams intake/carb setup (which are huge and awesome, but more expensive and will require more time, effort, and knowledge to tune.)