Made a 700 mile trip with the mods with no ill effect, so I jumped feet-first into Phase II and reworked the original 3.8975" water pump pulley to become the new alternator pulley; alternator should now be turning 55% as fast as stock (and 8% faster than crank rpm) if I didn't screw up the math. FYI original alt pulley is 2.13" dia.
I had to do quite a bit of tedious grinding on a motor mount that was now interfering with the path of the belt, and also on the alternator itself so that it would hug the block closer so that I didn't have to pry the belt on and off, but after the required bruising and bleeding, got it done.
So then, went on a 300 mile trip. No battery light =
! Tried to tax the system by cranking the heater blower full blast, headlights on, radio on, and tapping the brake to cause those high-draw brake lights to come on. Never did the battery light come on or any related issue surface.
Come to think of it, I should look into whether alternators are being spun a lot faster than they used to be. I noticed that v-belt driven alternator pulleys are far greater diameter than flat-vee pulleys... if the drive pulleys haven't also shrunk accordingly, modern alternators are being spun a lot faster.
No fuel economy improvements to report yet. It's going to be awhile before I can tell what effects this may have; first trip was through severe blizzard and awful AWFUL cobby rough ice that at times caused me to go 20 mph in 4th gear. Then after Phase II was implemented, that next 300 mile leg was into a 30+mph quartering headwind which, as we all know, really blows.
Also, as on my pickup, the Coupe now sports a fan delete, mainly because the radiator I put in doesn't accomodate the stock fan and I remembered that I've been driving that pickup with no fan whatsoever for quite a few years now. If she gets hot this summer, I guess I'll do something about it then.