Wheel specs are
here.
The bolt circle front and back is 4.75". Note that the front studs are 7/16-20, the rear studs are 1/2-20.
Currently Vintage doesn't make the FIA-style wheel but they've made the 427-style with FIA offsets to fit our cars.
Trigo makes a 5-pin FIA wheel but I'm not sure whether they can supply the correct backspacing. Their wheels for the FFR are close so a little extra backspacing is probably possible.