Unless you're dead set on keeping it all Ford, I'd pick up a inexpensive S10 frame. I believe your '47 has about a 110" wheelbase, and the S10 comes in either 108", 117", or 122". It also has a nicer front suspension for a rod, and they are plentiful and cheap!
I've known a few people who used them on post WWII Ford trucks and said the frame contours fit good. Most paid around $200 for a complete frame with suspension, and no engine or trans. Might even find a private party wrecking one out, and get it cheaper, and sell off what you wont use.