18" Pilot Super sport, which size?
 

Going with an XXR 527, 18x8.75 et35.

I am looking at these sizes:

245/35/18 92Y load rating
245/40/18 97Y load rating

I am lowered 1" on HKS hypermax, I am assuming neither of these size will rub.

However am I better going with a higher load rating and there for a stiffer size wall for track work?

245/35-18 is the right size. 245/40-18 is too tall.
Higher load rating does not imply stiffer sidewalls. The taller 245/40 will likely have softer sidewalls rather than stiffer.
Also, I wouldn't go with PSS, I got them for my FD and in my experience they suck for real world grip when not fully warmed up, and are only OK at the track. I'm going to replace them with RE71R...

Like poster above said, look into other tires if your worried about track duty

I have 245/35-18 on 18 x 8.5 +35 also 1 inch drop fit fine no issues with clearance at all. They are also the same diameter as stock size so you don't change the gear ratio.

I find them to be pretty grippy on the street and spirited driving, even autocross are ok. But yes like the others say they aren't track tires. High performance street.