100% IMO
I think a calendar of this nature would definately elevate the interest of the male 16-45 category!
Would I pay $20 bucks for one? Maybe, but I'd get paid a shot to the back of my head if its too far on the "tool girl" side. Although it would be ironic for a bondage model to be sqeezed underneath a 914 trying to hook up the gear shift linkage, or disconnecting a dashboard.
The reality is that there are plenty of 914 owners out there. You might get a larger distribution channel if its tastefully done. You can decide for yourself if the cost is worth the risk.
It may seem sterile, but w/o the chicks it would be a definate buy for me. I'd enjoy being reminded monthly of the heights that various 914 owners have built up their cars, and would proudly display it at work and home.
Maybe chicks sprawled across 914s could be a bonus feature. Even if they're wearing clothes, it changes the focus of the picture and I think, limits your market potential.
I appreciate the entrepreneurial spirit though, keep it up!