First of all if that motor does not have a heavy cast flywheel it will not work very well or if at all for what you are trying to do.
This mumbo jumbo about stalling out is just that, get a rheostat for the field wire on the alternator and adjust the field as necessary.
Car alternators are best for these types of applications because they take the vibration of the motors well. Most likely you will mount the alternator as if the shafts were joined by a coupler to acheive the proper rotation for cooling, check your fan and be sure.
I've been building these since 1980 and they work great, I can't beleive the naysayer posts here on this one, you can get a great charger from these, alternators were designed to charge batteries.
Let's get a little more indepth, generators are a great way to go also, from tractors or old cars, buy them rebuilt, it will cost a little more but you have the ability to also start the motor plus put 20, 30 or more amps into the battery. Combining the 2, alternators and generators on the same motor can be a benefit too but you have to do some calculation on the pully sizes, you can get the generator to start the motor when the battery voltage drops to a point.
Best thing to consider is the rpm, I have built some where I put a pulley on the engine that is the same size as the alternator giving a 1:1 ratio, at about 100 rpm you can get a 3rd or so of the alternators rating and the motor will run all day on a few gallons of gas.
The Honda's I buy now are pressure washer take-offs with low hours, they are fuel efficient as hell, especially run at about 1000 rpm, quiet with no vibration, you can get them for 120.00 if you look around and they last a long time.
get an inverter as some have suggested, don't try to put out 120 or 240 from these setups and buy at least a 4.5 HP motor.
If you decide to crank it up to 300 rpm, a 5 inch pulley on the motor is about right, try the 1:1 method with a rehoastat, you won't be dissapointed, but you won't get the alternators full output either, but great for charging batt's.
Hope this helps, I run my cabin and my boat on a setup like this.