Just last week I put and xtra 12 into a 1990 440 sport.. I put the skid as high up in the tunnel as possible and it turned out great.. Rides much better the the stock suspension. By tucking it up in the tunnel I was able to keep the stock front end. Ended up raising the rear of the sled by only 3 inches.
If you want I can try to get the meausrements, but I know I got them on here somewhere..
Off the top of my head I want to say that the front mounts where 6 inches back from drive shaft, and then 23 inches center to center to second mount. I made my own front mounts 3x4 inches, and used 6 rivets on each to hold into place.
I also did an xtra 10 into my 94 xcr and I must say much happier with it. But the way I ride I need the 10. They way the sport gets road the 12 is fine.
1997 XC 600
2004 Sportsman 500HO
Parting out 1993 XLT and 1997 XCR 600