I love experimenting with ways of using current instant print films in older instant cameras or backs or even just jamming a sheet in the back. I have some 405 and 545 backs and still a few packs of film but have been experimenting with Instax, the colour fidelity is so impressive and is the best instant film available except the B&W where the current Polaroid stuff outshines it.
I just acquired a Polaroid 180 and worked out that you can place a sheet of Instax Wide in an old film pack holder (have loads as I never thrown anything away) then I process it in a Fuji instax wide camera I bought for parts but works fine. I experimented a bit further and created a sort of film pack with one sheet in the open aperture with the pressure plate back over it, then a pile of 3 or 4 more sheets on top of that. You need a changing bag, but can then shuffle the sheets between shots, sort of a bag mag style, then take the lot out, place into an Instax cartridge and process in the Fuji camera.
I have just found on Thingiverse a 3D print design holder that will do one sheet at at time but with a dark slide so you don't need a changing bag between shots, just a load of the printed holders with the film then transfer to an Instax camera for processing.
I also tried a sheet of 1/4 plate film in an old holder, fits ideally, and that worked great and again have seen a 3D print design for a back to fit a Land type camera, which would mean no messing with the focal plane and lens position and rangefinder adjustment.