Well . .
I pulled out my COLREGS and my situation requies 2nm lights (1nm for sidelights). Annex I translates that into 4.3 candelas for 2nm and 0.9 cd for 1nm. (4300 mcd and 900 mcd respectively.)
The LED's that fit into the old standard recepticles can do 8200 mcd!! This exceeds the instensity requirements for my boat. However, the two bulbs I'm looking at have a fan of 12 degrees or 100 degrees. Not quite what I need for sidelights or the stern light.
I have found some bulbs at the local West Marine that fit into my sockets (see 10956 on pg 569 of the 2006 cataloge), but now I am doubtful as to their application in my sidelights because of this possible limits in the horizontal plane. Tomorrow, I will try to install a couple and see what happens. Stay tuned.
All this might be simpler if I went out an purchased and installed a new set of those fancy sidelights with the LEDs already in them.