GM Delco Alternator

I picked up a GM Delco alternator for a project recently and I am having a tough time finding what pulley sizes to use. It is a 10si type, however it is a 3 wire and I plan on keeping it that way. It has the standard 2.5" pulley and it's a 63 amp. What I don't know is what size pulley should I use to drive the alternator. I plan on pulling the governor out of the engine (Briggs Vanguard V-twin 16hp) and putting in a billet flywheel and rods. I know that the alternator should not spin above 18,000rpm, at least according to hot rod magazine's article. Just not sure what size pulley to run on the engine that wont allow it to be over spun.

Also what gauge wires should I run on these? Was thinking 4gauge off the battery and 10 gauge off the jumper and idiot light.

With a 2.5 inch pulley and you do not want to spin faster than 18K rpm.  You are talking billet, so let say you are going to max your engine at 5000rpm, then the largest you can go on the engine for the alternator to max at 18K would be a 9 inch.

Cool little page to figure that out...

https://www.blocklayer.com/pulley-belteng.aspx

With a fully modified Vanguard V-Twin what is the highest the engine will spin? I was thinking 6000rpm tops.

Maybe so. I was keeping it simple. I hear they can some of these engines up to 10k.

I'm just trying to keep it limited because I'm getting a 780 CVT for it and that's limited to like 5k rpm.