Help me decide - Big or small bolt pattern?

Functionally, there's nothing wrong with staying with the small bolt pattern, and the factory small bolt pattern Kelsey/Hayes disc brakes are arguably better than the later large bolt pattern disc setup. But as previously stated, wheel availability comes into play; as does parts availability- which is already kind of dicey here in the U.S., I can only imagine how it is in Sweden.
A possible compromise is offered by Dr. Diff: A late A body disc brake system with small pattern rotors. The best of both worlds- parts availability and keep your small pattern.
10.95" Front Disc Brake Kit (Stage 1)
The only possible issue that I see with this kit is the hub diameter. Factory small bolt wheels have a smaller center register than the large bolt units, and I don't know if the register on his small bolt discs have also been reduced appropriately to fit factory steelies (not an issue with aftermarket rims, since they are not usually hub-centric). Call/contact him to confirm this. An added benefit to this (in your case) is that the late disc setup widens the front track about 3/4" on each side, possibly eliminating or at least reducing your desire to run wheel spacers.
Edit: One other bonus is that if you ever do decide to change to large bolt circle, all you'll have to do is get stock late A rotors, and you're done.