Have been building and useing SI alternators since my High School days. We have converted every old tractor in our line-up from 6 volt to 12 volt using them. I converter every single older vehicle I owned to them as well. They are stoopid simple to rebuild, no special tools needed. On some set-ups you'll need to install a diode to keep them from back-feeding.
I'm NOT a fan of the one-wire variants. Tried a couple over the years and found that it is just better all the way around to use the standard 3 wire system. On retro-fits we simply jump from the BAT terminal on the back to T2 on the regulator. The switched wire goes to the T1 terminal.
If you are replacing an older alternator with an external regulator you can jump the wires in the harness and leave the external regulator in place for the original look.
Google "GM SI Alternator Wiring Diagram" and there are some good photo's of how to hook one up.
For parts there is a source here in Ohio I've been using for many years that sells complete rebuild kits with USA parts in them. Never had a single issue with any of those parts to date.
https://www.ebay.com/itm/193306550715
https://www.ebay.com/itm/191103912028
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https://cliffshighperformance.com/
73 Ventura,
SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),