re: My next-door neighbor now has three "project" cars

pretty simple fix if you ask me. Next time he is out by the project, just calmly approach him and begin a discourse about the car. An example may be

"Hey, Boats n' Hoes....you been working on that sweet arse late 90's model mustang for a while now. What's that thing worth man? I got a huffy bicycle I'll trade you for it...."

and then, now this is important

toss this in the passenger side window