I think I need more cam

If you are planning mostly race, then by all means go with a cam more suited to what your plans are. You have large decent ports, and are planning a large plenum high flow induction. You can under cam that too, and it will run decent, but IMO you should be looking into solid flat tappets in the 250-270 @ .050 range. You didnt say what the compression comes to, but with 53cc chambers, I'm thinking in the 11.5:1 range? I would go for something like the Comp TL300S-8. You need not fear to rev that engine to 6500rpm. With 3.23s, you wont be revving higher than 6K anyway. The stroke is 20+% longer. So your power band will be lowered by at least 1000 rpm in terms of what you read for intended applications in catalogs. Plus, your intake will be sized for mid range and hgiher rpms. I dont think that convertor will be good for you, but that you can always address after the egnie is running and you know what it wants. I would be careful if you are making your own intake as far as runner volume and shape, and plenum volume. It's not just a big box up there. You can have some bad distribution issues if you are not very careful. As for carbs, "two small ones" in this case could be a nice set of 660 race center-squirtors. I wouldnt run under 1200 total cfm for a dual quad system. And if you decide to go single, the starting point would be a 930 HP Holley and a Victor 340. I know of similar built flat tappet 416s that make 530-550hp on a regular basis. A solid roller could push that over 600.