I know most on here talk first gen cars but I saw a '91 RS with auto for sale today with only 62K miles on it. It was very clean no rust.
What are the pros and cons of the '91's. What should I look out for?

I dunno. Is it a 350? Did you search thirdgen.org?

Con: Accessibility of #8 spark plug.
Con: 7.5 inch diameter rear gear, usually 3.23 ratio. Look for G90 on glove box door, this will signify posi, er, limited slip.
Pro: Speed density EFI
Pro: Quick steering
Pro: Fun to drive.
Con: Metric studs on wheels.
Con: Front wheels have different backspacing than rear wheels, I think.
Pro: Fun to drive.

I had a 85 Z/28 TPI with 89 Corvette 350 and auto. Kindda wished I hadn't sold it. Now I have a 2005 BMW 325 convert for a "go-to-work" car.

The sub frame is prone to cracking up around the steering gear box. Had to have my 85 welded because the torque of the gear box was flexing the left side. The only fix is to have a brace welded in between the 2 sides up around the radiator to minimize the flexing.

I owned a '91 RS 305. I loved it. Sold it after 120,000 miles. Never had any major problems with it, but I didn't abuse it either.

Everett: "Con: Metric studs on wheels. ". What did metric studs do to you. :)

"Con: Front wheels have different backspacing than rear wheels, I think." - yes, on the 16" wheel. Big con there is inability to rotate. Nice set of aftermarket rims cures that.

CA, I wonder if that cracking is what those 'wonder bars' (i understand they tie the front of the sf together) the 3rd gen boys talk about are for.

Everett: "Con: Metric studs on wheels. ". What did metric studs do to you. :)
Since I had none at the house, I had to make a trip to the store to buy some for replacement. Now I have another bolt jar for metric nuts, good thing I have Buford, 88 M/Carlo SS.

"Con: Front wheels have different backspacing than rear wheels, I think." - yes, on the 16" wheel. Big con there is inability to rotate. Nice set of aftermarket rims cures that.
What is the difference dimensionally between the two wheels?

Since I had none at the house, I had to make a trip to the store to buy some for replacement. Now I have another bolt jar for metric nuts, good thing I have Buford, 88 M/Carlo SS.:)

What is the difference dimensionally between the two wheels?I dunno, I’d have to look it up. I don’t think it is more than ½” backspacing.

well if its got the 700r4 trans then a rebuilt one will run you bout $1100
con-torque arm on tranny to rear end allways breaks rubber mount,is it a t-top car? even new seals will still leak
a pain to run true duall exhaust

These cars are a great buy for the money right now. The RS model does not have the Torque arm, quick ratio steering and unlikely to have TPI or Posi rear-end. My rec is to buy a 91 Z/28. They are fairly fast, fairly rare and get good gas mileage. Reliability is good. I have 3 92 Z/28's which are the same as the 91's and am very happy with them.