Tire fitment question for 987

[MikenOH]

I've got the 18" rims and currently have the PS2's (265/40/18) on the rear. I've been looking for a replacement set for track duty but here is little in this size except for the Ps2.
I' thought I'd try the Falken 615 or Toyo RA-1 but they only come in 273-35-18. When I tried to order the salesperson asked if I knew for a fact if they'd fit since there were not returns on mounted tires.

just by eyeballing it, I would think the extra .3" tread width should clear but who knows how the new tire is sized relative to the PS2.

Anyone on the board using a 273/35/18 rear on a 987?
thanks for any help.
Mike