Welcome from New England! Nice truck!
Your truck being an '88 is called a V2500. 1986 and earlier a 4x4 3/4 ton truck would have been a K20, in 1987 they switched from C/K (C for 2wd, R for 4x4) to R/V (R being 2wd and V being 4x4), so my '87 half ton is called a V10. Then after '87 for the remaining years of square body trucks they switched from the old 10, 20, 30 numbering scheme to the familiar 1500, 2500, 3500 they still use today but kept the R/V because they didn't want to confuse people with the new C/K line of pickups (GMT400 body style)