Luke,
Is there some sentimental attachment to those old truck parts that makes you want a knife made with it? The best old truck part you can use for a blade is the springs. The rest would just be a lot of work that might not make a good knife. The springs, at least, have good potential in the right hands.
Let's say there is a sentimental connection with a particular vehicle. You'd have to ship the piece to the maker. If you get someone that is willing, you might be prepared to cut the stuff into pieces to ship. To answer your question, yes, it's possible.
BTW, I wont be able to do it. I got a lot going right now. Glad to see you here Luke.