So the PI Taurus uses a 245/55R18
Those are some aftermarket center caps, not OE as well, so those don't add value on that set IMO.
The wheels are reps, but not even GT500 reps, seller doesn't really know what they are, and just put that due to the center caps most likely (A LOT of cragislist mustang wheels get listed as the wrong style because people are told something wrong, or they have a different center cap, and people don't know)
The front tires, are .6" shorter, and .4" wider compared to the PI OE Size. Speed would be slightly off (~1.5 mph at 70) with these on all 4 corners.
https://tiresize.com/comparison/Rear tires are .4" taller and .4" wider compared to the PI OE size. Speed would be ~1 mph off with those on all 4 corners.
Between the front and rear tires ON THOSE RIMS, the difference is 1" in height, and same width. There is a difference of 3.6% in circumference. This COULD cause AWD issues if you ran that tire size.
IMO I would tell the guy you wanted to look at them, assuming you like the style, and they finish isnt damaged (no curbing). Go with $400 cash in your pocket and make that your max. I'm not sure if the way its listed means the rears have 25% life left, or 75% left.
You would almost assuredly want to change tires to run on the SHO. Depending on the rim brand they could be good rims that cost $200+ per rim, or they could be really cheap that cost 80-100 per rim, or intermediate like the AMR.
If you want to, ask the seller to get you pictures of the inside of the wheels, all of the stamping. There should be some stamping saying size, to confirm 18x9. There should also be stamping to help determine manufacturer.
I'm fairly certain those are silver AMRs or similar from what I can see of the spoke patern. Offset is likely 35mm which will fit fine on the SHO but again, wont be identical to your stock setup.
If you aren't hard pressed to get the wheels rn, I would wait or knock the guy down in price. I've seen the stock Bullet style wheels for $200 with really nice tires on them. Again its totally your call but IMO those aren't worth $600 second hand. It also doesnt mention tire brand, so they could be cheap