For a small block there are a couple of options. Visit FOR A BODIES ONLY web sight and go to early A's. There are both long tube and shortys made that will fit your car. There are sets of long tube fenderwell headers in 1 7/8 that fit a 1970 Cuda 340. I had a set, acquired from a guy that traded his smallblock stuff to me for my 440 race motor to put in his Cuda. I put them in my 65 Dart when I first got it with the small block 340. They are Hooker, slip together with different pipe length combinations, and 1 7/8 primarys. These would produce the most Hp if you are able to find a set. My idea of a cool early A is a stroker smallblock with a 440 cube size. You can say you have a 440, and you do. heads available for the small block are vastly superior to what came stock on a 440 BB, so you can make some very serious power.