Leak in Carburetor

I had the same issue with the thin carb base gasket, my kit came with two different gaskets. I used the thicker one like I have in the past with my Darts. As for the bolts, I had one long and one short, fortunately I have a hardware supply from past cars that I use every now and again, and I had the correct longer bolt in stock. Having the carb held down by two or three bolt threads, I would be more worried about having the carb come loose and twisting enough to jamb the linkage open while I'm driving. Any bolt is better than what you have now, they don't have to be hardened because your not going to wrench them down like lug nuts, you just want them to be tight to hold the carb in place. A good auto parts store should be able to get you the correct bolts that you need for it at a reasonable price.
Paul