has anyone got a spec flywheel for a st170/svt to had that they could do me a massive favour and just measure it for me

im after the diameter of the ring gear please, with a ruff eye and a engineers rule i make the standard item 285.5mm

and my shinny spec item to be 287.5mm making my starter whine its tits off,

trying to determine if its a mistake by spec (as they say theyve never had a proble over the decade theyve been selling them) or ...... pass iv run out of ideas lol