The 2 local regions I race with have recently started running street tire and an open tire classes. That is, if you are street tires in a class that allows race rubber, like stock SP and so on, you are in the street tire classes. If you are on race tires or in a ST class you are in the open class. Its geared to let the weekend warrior to be competative and to get noobs to stick around.
I'm seriously thinking of ditching the Rcomps when my current set are done and just go to streets.

I will stay in BS. I want to know if there would be any benefits to running a 265/35-18 over a 245/40-18.

It's going to depend a lot on the tire. I went from a 275 to a 255 this year, switching brands at the same time from the Azenis to the new RE-11. The RE-11s are a huge improvement, even at the narrower size.

And which size works better will vary from tire to tire. If you're sticking with an 8" wheel, to stay in stock, I don't think I'd put a 265 on it.

Sadly, some of the good street tires cost almost as much as a set of r-comps. They just last a lot longer. :) Well, they still have tread after a huge number of runs. Whether they're heat-cycled out is another question. :)

I'm with Pockets, I wouldn't run a 265 street tire on a 8" wide wheel. I'd look at a competitive tire in a 245/40-18 size (Kumho XS, RE-11, AD08, Star Specs, etc)

Reasons? Too much role?
Not arguing, just asking.