If the engine has been run after the new plugs were installed, but before the regulator was changed; there is a possibility that the extremely rich fuel mixture from the bad regulator has completely fouled the plugs. Try removing a few plugs and looking at them. If the center insulators are black, then the plugs will not fire. They will either have to be replaced, or cleaned with a bead blasting plug cleaner.
If the plugs are not the problem, there is a possibility that the coil or coils are defective (even though you may see a spark).
Another thing that may have happened is that the timing chain has jumped. If that has happened, it will cause the compression to drop way down. Try running a compression check on the engine. If it is out of spec, then the timing chain has probably gone.
I hope this helps!!!