Paul,
     since my motor did not come with an alternator,
just what size should I be looking for ??  Neil.


It depends on what you are going to do with the
airplane. Flying at night will require landing
lights which can be up to 100 watts or more.
That is 8 amps right there.

You need to decide what
you are going to put in the airplane and add up all the
amps. A big consumer of amps is the high pressure
fuel pumps. That is several amps right there that
varies with brand.  I think most automotive alternators
put out about 80 amps. Radios and moving maps can
suck down some current as well.

Paul Lamar