externally the 301 and 400 are the same so you can use all of your valve covers, pulleys, timing cover, valley pan, etc and it will bolt in just as the 301 did. The th350 will bolt right up and will also fit in the same manner as it did witht the 301. For carb help, I like QJ's personally. An option could be just to block off all of the vacuum ports you aren't going to use. As far as intakes, the edelbrock performer is the only one that I know of that you can use and still retain all of the original shaker mounting items but you will not gain any performance with this intake as opposed to the original intake. Carburetor choices also have to be made wisely if you plan on using the stock shaker setup.