I ran solid roller lifters and roller rockers with a custom high pressure valve spring setup - I would do something similar again for a competition motor. It takes a little machine work but you can make some very nice high quality solid lifter components from other engines fit into the 7.3 block - the popular choice right now by the mechanical crowd is a particular lifter built by Jesel for what ever reason - probably one guy did it and they all copied. I am not sure that I would run the Harland Sharp rockers again (WOE) - but I would find/source some that I would feel comfortable running. When converting over to mechanical you have a TON more room to work with... I would probably look at some shaft mounted rockers instead of individual pedestal mounted ones.
Good luck and get ready to fab and make fit pretty much everything.