I've done that a couple of times. If you have stock exhaust manifolds, this would be the time to remove the restriction at the exit end. Also, pre-fit them to the heads before you put the heads on. They tend to change shape when you remove them and you need to relieve the forward and aft mount holes. Do not change the mount holes for the centre ports.
If you have adjustable rockers, you need to set them up correctly. I believe that Dave Dalke did a post that explains the procedure that he uses. It is critical that you do that right.
Change the oil! Run it a bit and change the oil again. You must get the antifreeze out of the oil. Yes, it will go in there!
You should contact Dave Dalke to get the part numbers for changing over to ARP studs. The stretchy bolts kind of suck.
The rest, as far as I remember, is straight forward.
Crap, wished I would have known about modifying the exhaust manifolds before I replaced the headgaskets in my 1991 and 1993 SC.
if better exhaust flow is the goal, this is also a good time to swap the passenger side manifold for the later '94/'95 style. This change would of course dictate a pipe mod, which is a good excuse to move to hi-flow downpipes and cats.