Tell the parts guy... Well just swap the pulley yourself. Use an impact and knock the nut off and back on to swap them. Hint the Gasser pulley is smaller than the diesel pulley. It is usually visible. Turn your core in without a pulley.
You could also find an auto electric shop that rebuilds starters and alternators and they can swap to the proper size on one of their new or rebuilt units. Rebuilt CS-144's are better than the CS-130's by design. So far I have had great luck with rebuilt CS-144's - not the best option, but, good enough esp. vs. a new cs-130. The best way to go is all new.