Thanks all for the help and tips.

I downloaded Longstreet and i will take a look.
The perry rules are those included on the plastic boxes?
Paul, glad i´m not the only one with this idea.

I´m going to opt for 20mm because i already have the miniatures in metal.
However i´m also painting some in 28mm for squirmish games using the Ganesha rules 61-65.