Just finished converting an old Polaroid 110 Pathfinder to Instax Wide using the Lomo Bel Air back. The finish is still a bit rough but it's perfectly working now. I'm glad to have an instant camera that uses easily available film, focuses accurately and has user-selectable shutter speeds and apertures. It's also purely mechanical and needs no batteries, even for the meter. It's a thrill to use but a bit heavy. Kids and adults around me always find the instant film magical.
I started with by checking out instantoptions.com for info on how he did his conversions. Opted to do the conversion myself since I'm in another continent. Check out his work, he makes really nice stuff.
Once I got the Polaroid 110, I removed the lens and cut off the frame to allow for clearance of the wind crank of the Instax back. I also remove the Polaroid's back and cut it off to accommodate the new back.
I prepared the Instant back by grinding out the plastic bits that were jutting out, making a flat surface to adhere to the Polaroid. I used a combination of body filler, adhesives, magnets and screws to attach the back to the polaroid body and make it light tight.
Once attached, I calibrated the lens and standard to match the back. The film plane has to be moved back a few millimeters. Ground down the rivets on the front standard and moved the front standard to match infinity focus on the back. Good thing the rangefinder still matched the lens and didn't need any further calibration.