I am far from being a instant cameras specialist and I am a bit lost with the different film formats, back formats, etc... Hence the following and simple question: Are The Fujifilm FP-3000B and FP-100C films compatible with the Polariod 100-400 series packfilm cameras without adaptation of any kind?
My experience is yes, the films fit into those cameras properly -- I've used both in my Polaroid 180 and a 400-series camera. Given the differences between different Polaroid models, you'd want to verify if the camera you select can properly handle very fast film like 3000B.
The only issue you may see is that the new Fuji packs are plastic so if your Land Camera has a built in timer on the back, it might push the pack a little and make it hard to pull the tab/film out. Replacing the plastic Fuji pack backing with an older Polaroid metal pack backing everytime you change packs might help.