The “$” is the trademark logo of the Wyman-Gordon company, the company that made the raw crankshaft forgings for Ford. It’s actually not even a dollar sign, it’s a symbol that has another name, but I don’t remember what it is actually called, maybe someone else remembers.
Is there an engineering number on the crankshaft? Often it’s hand stamped on, or partially hand stamped. Does it have an “SK”, “ASK” or “XE” number on it? Any pictures of the crankshaft rod journals? Full picture of the crank?
It’s certainly possible that Ford could have made a few 3.98” stroke forged cranks from raw forgings, maybe for the Drag Team members, having something like an “SK” number that matches some Ford documentation would be nice. You might want to check with Jay Cushman at Cushman Competition in Maine, he has quite a collection of rare Ford parts, as do a few of our members here.
People have offset ground 391 FT forged cranks to 3.98” stroke cranks also.