Billy,
I fitted 4x4 front discs & 2wd 4 pots to my series one when i had it with no problams at all. I was also running on standard S1 wheels. The only thing i did use was a 2.5mm washer between the caliper & mounting point to centre the disc in the caliper. BTW, Your picture shows the caliper mounted on the wrong side of the mounting bracket. You need to move it to the outboard side (ie between the hub & strut, not on the back as you have it) Don't give up mate. You have bought the bits required! Where there is the will there is always a way.
HTH
Andy