There will be a heavy surge current immediately after startup to recharge the battery from the drain of the starter. Once that is accomplished the alternator will only produce enough current to meet the load of the ignition, lights, etc. and keep the current going into the battery high enough to maintain the voltage at whatever the electronic regulator is designed to do. Usual current flow into a fully charged battery will be around 5-10 amps, regardless of the max capacity of the source- - - -generator or alternator. Upsize at least one wire gauge on the main charging lead over what's needed to handle the smaller alternator- - - -maybe 8 instead of 10, for instance.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!