diana, my best advice would be not to spend one red cent on trying to get more performance out of the 256 Y-Block motor. It will, however, make a great anchor if you own a boat. It's a little heavy to haul aboard, but with a little thinking, you could mount a battery powered winch.

Just kidding, but seriously, 1954 was the first year of the "new" Y-Block. It wasn't a very efficient motor and was discontinued in passenger cars after 1957, with the final displacement of 312 cubic inches. Ford continued to put them in pickup trucks for a few years after that, I guess to just use up the inventory on hand.

As far as custom modifications to the body, that's entirely up to the builder, that's why they're called Customs.