Are you rewiring anything or just switching to 12v 1 wire alternator? As for the 10-SI I'll second hotrod. I put one in my truck and even with 3 flood lights, 2 emergency lights, headlights and siren it's able to keep up.
There are posts on here about changing over, just do a search, I've also included a different sites nono 'tech tip'.
conversion


1952 Chevrolet 1700 Bickle Seagrave
"Old Smokey'"
Following the build in the DITY Gallery