Actually, the rear tire off the Prowler is a Goodyear EMT, and it's the same size as the rear tire on the SSR. BUT it's over TWICE the cost of the RS-A you would replace.
The problem is with the front tire - there is no P255/45R19 run-flat tire available. If you were to replace just the rears with EMT's, you'd be mix and matching tires, and that's usually a huge no-no. Without tire characticstic measurements, there's no way to really predict how your handling might change with mixed front and rear sets - as a vehicle dynamicist, I'd recommend strongly against it.
And freezer is right, the rear tire would be some ultra-hi performance summer-only, park-it-in-inclement-weather tire. A light dusting of snow would immobilize your SSR, were you to acutally install just the rear EMT's, not to mention the unpredictable effects on handling.
Shame about the flat tires, sarajohn. Use that great handling and dodge them potholes! :lol