The pace cars came with "Goodyear GT Radial" tires. They are raised white outline style, not full white say as with the current "Goodyear Eagle GTII" tires.
The original style tires are no longer available through Goodyear or any of the reproduction tire companies such as Coker.
I've seen some "Goodyear Eagle GT" tires with the raised white outline style. I don't know if they are the correct size or if still available.
Many folks have talked here as to what tires they have chosen for their cars. I will be putting a set of "Firehawk Indy 500" tires (made by Firestone) on our pace car in the next couple months.
Take care - spring is on the way.
GaryC - Franklin, IN - '78 Pace Car replica