Terry - PPG's Deltron DPS 3055 is their version of a typical, modern day, 2K (2 component) urethane surfacer. Just about every paint manufacturer has a similar product, the main difference being price. The Corvette shop you mention, I would imagine, is familiar with this PPG product, therefore, they recommend it. The 2K surfacers are my choice for every car I restore, in fact, the Darrin (#145) I completed last summer is wearing it! And, it sure beats the heck out of the stuff we were using in the sixties (for body repair, I mean)!!
Gary (darrin145)