G'day all,
Spur sprockets are the cheaper option, and they're available in 3/8" pitch for that saw; e.g https://www.outdoorking-forum.com.au/index.php?main_page=product_info&cPath=95_1029&products_id=7445

As billyj says, you'll also need a new guide bar, to go to 3/8" pitch chain.

All up, not really worth it for an occasional use saw, I'd say, when you can buy some serviceable cheapie chains from Jono & Johno @ $24 each or 3 for $54!
https://www.chainsawspares.com.au/?rf=kw&kw=325+050+66dl


Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."