You didn't.
Although plerbl said "maybe get rated for PA28-181 or possibly to an Archer" I assumed what he meant was 'possibly to an Arrow' because, as you say, a PA28-181 and an Archer are the same aircraft.
Either way, the WLAC fleet includes PA28-161 (Warrior), PA28-181 (Archer) and PA28 180R (Arrow).