that is the correct method, and it makes no difference which you choose
as the negative or positive, other than it is easier to keep track of
if you assign the negative one that is closest to the negative output post
on the alternator and same for the positive.

the rotor can take up to about 7amps, but i would stop way short of that
in testing they do very well at 3.5 to 4 amps, so i would limit it to 5 max.
to keep down unnecessary heating.

i assume you are going to charge a 12volt battery bank?

i would expect you will make 80amps with a 5.5 hp gas engine if you have the ratio
worked out, the cut in for that alternator iirc is around 8-900rpm  and to get to
about 80amps or so you have to turn at about 2000rpm? i would have to look it up again to be sure,, but am reasonably certain i am close.

i would suggest driving the alternator at ~2200-2500rpm while keeping the engine
at full rated rpm which i assume is 3600rpm, so something on the order of a 4" engine pulley driving a 6inch alternator pulley is probably pretty close. figure on using either a twin A belt or a single B belt, and if you can use either an AX or BX
notchbelt which can handle a bit more abuse.

not know exactly what your needs are, you might just connect the alternator using the oem regulator and see how it works as is? if you keep your ratio correct it should do a good job as is,, the only mod i would make is putting a switch inline from the regulator to one of the brushes so you can start the engine and get it settled and warmed up before the load hits it,, otherwise you will never pull start the engine.

don't worry much about hurting the alternator, it will tolerate running without even being connected to a battery without the output rising above the regulator setpoint, and can tolerate having the battery switched in and out while running as well,, probably not recommended but it will tolerate quite a bit of baffoonery that would kill most other regulators if not the alternator itself.

you picked a good alternator that will deliver excellent service for a very long time, with good efficiency in about the 80amp range, above that the efficiency starts to drop a bit at 100 and drops more above that of course.. lower efficiency means more hp needed to drive it.

like i said i think it will make 80, and it might do 100 with your 5.5hp engine if it is in good order.

look forward to how it turns out for you.

this is the correct method for connecting a reostat control if not the preferred method which would be a purpose built controller such as a balmar or xantrex, or similar that can tailor the amps out and in doing so match the alternator to your engines ability to drive it.

Thanks for the speedy reply!

We will see what it can put out. I screwed up ordering the pulleys, so the choices I have are a 3.95" and a 2.55" pulley. For starters I'm planning on putting the 3.95 on the alternator and the 2.55" on the motor, trade a little RPM for torque. They are twin A belt pulleys.

I have a uC controller I built, but the current sensors only go to 50 amps, so I can't use it until I get some better sensors and twiddle the programming. For now I want to use the above method just to play.

It's my birthday, so I get to play with my new alternator all day if I want!