I have a 93 4-door with Jeff's spacers.  If I understand correctly OME springs are about an inch taller than stock springs so can I run OME 4-door springs with a Calmini, bits for vits, or home made diff drop?  If so are my struts long enough and do I need rear diff spacer?

You can run any of the diff drops with any of the springs.  You need to run the diff drop with the taller springs, and definitely taller springs and Jeff's spacers.  If you are doubling up on the springs and spacers you will want to add Jeff's strut sapcers, may want then with just the taller springs.  Without the strut spacers you will find out that there is only an inch or so lift left before the strut bottoms out.
You may find with the taller springs and spacers that when stuffing the front suspension that your brakes seem to not be there on first stroke.  If it does that, see how much bow is in the springs.  Mine were hitting on the brake caliper and pushing the fluid back out of the calipers, resulting in no brakes for first stroke.  (Doesn't seem to happen to everyone.)  I raised the outside of the spring pad to make springs sit straighter, also getting another inch of lift.  Others have dropped the inside of the spring pad (which decreases your lift?).  If it happens, its nice to have an idea on why the brakes are not always there.

I'm one of those who dropped the inside of the spring pad, and BRD HTR is correct, I did loose a bit of lift and had to compensate with a spacer. If I were to do it again I'd do it his way. It is worth it to straighten out the coils though.

Thanks guys, I was just worried about cv angle.
BRD HNTR, I have Jeff's strut spacers on allready.  I read your write up on the bowing coils, maybe I wont have that problem.