Ferrari trademarked F40 as a symbol, the top line of the upper case F as it extends over top the numbers 4 and 0, which is limited to "SPORT CARS AND STRUCTURAL PARTS THEREOF". You probably shouldn't use it that way. I met Wayne Carini a few years back as I traveled thru Connecticut at his car dealership, F40 Motorsports. Awesome TV show if you can catch an episode. Digital Equipment (then Compaq, then HP) had a GT40 computer back in the early 70s. Fender currently builds an entry level small guitar amp called the MUSTANG GT40 - take that Ford and Safir.
Ford has at various times owned and released the GT40 trademark as it appears on certain items, like textiles, gadgets, decorative crap - anything a marketing company would want to capitalize on.