What's so wrong with the calipers that you need new? I had one '71 crack a 
chunk out of the cylinder bore, wierd, it was scrap.  But despite rusty 
exteriors, busted off bleed screws and lines, I rebuilt my '72 calipers for 
something like $12/ for a seal(/dust cover/O-ring?) kit, and bought a hone 
to do the bores over. That was the rebuild extent. (The master cyl kit cost 
$8 at the time.)

  If the pistons are badly pitted you need new ones. May get up to the price 
of rebuilts if you can't find a nonVWoA source, :(.  Also rebuilt calipers 
on '66 Porsche same way, no probs, and they were fully siezed before I 
started.  Use toothpaste or Brasso to polish up the pistons, go easy on 
emery cloth, bit coarse for this job. Buy some brake-cyl. grease/paste for 
assembly.

   Tim Smith