I think you need to figure out what size tires you want to run first. Maybe it is just me, but sure seems like the hard way to do it.
To (kind of) answer your question, after searching on a size, I usually filter on the EPS, MPS, UHPS and maybe HPS. Most of the AS categories seemed to result in tires with a 500+ wear rating and I am looking for more 300ish. In theory, 300 should last a couple of years but be sticky enough, while a 200 wear rating seems like it would probably wear out in a year with a decent amount of driving. I don't usually look at speed ratings as the category seems to filter it down to the higher ratings, but I would stick to H or better if possible.
Some thoughts.
Sticks in my head that dropped spindles limit your offset/backspacing. And that really limits the tire width? I don't remember what the limit is though.
My target for sidewall height is about 4", but it's kind of an arbitrary number. IMO, 4" avoids the rubber band look and still give an aggressive look and a stiff sidewall.
A good all around tire size seems to be a 245/45R17 which has about 4.3" of sidewall and enough wheel diameter to push the wide tire into the wheel well without crashing with the tie rod end. Add that a 17x8 Mustang wheel is cheap and easy to fit and it just seems like the best all around option (IMO). FYI, I have $90 in the 4 wheels '97 GT 17x8 wheels I have.
As a comparison, I found (3) 225/50R15 tire in the performance categories on TireRack and 2 of those look like track tires. Plus, those are a pretty short tire (23.9 OD) and doesn't have any more sidewall than the 17" tire I mentioned above. The next 225 width tire was a 225/60R15 and it had exactly one option, the BFG T/A. A 225/50R16 tire has (18) options, or (29) if you add in the performance AS category. The 245/45R17 has (22), or (42) if you add PAS the category.
