Well, I'm reaching way back here trying to remember these things cause they were more of a pain than anything.
Seems like most of the mounts just clipped on the barrel, barrel facing up. Problem we had was mounting the rifle like this took away room and hindered getting out of the vehicle.
The clips were, how can I describe it? Probably about three inches long, and one side of the clip was contoured so the rifle barrel would slide in and was under tension. The clips were dipped in Plastikote type stuff.
I hope that helps. If there's not further on this by the time I get home from work tomorrow, I'll go into Photochop and draw ya a picture of what I can remember.
For an AK or something, as long as the mount was at a height to accept the barrel and keep the stock on the floorboard, then it should work for ya. But instead of mounting it on the outside near the door, I would go for something in the middle. Or better yet, something above your head.