The 1999 GMC Sonoma is available as a 2-door, 3-seat regular side. Starting at $12,368, the 1999 GMC Sonoma SL 4x2 Regular Cab Short Box is powered by a 2.2L , 4 -cylinder engine mated to a manual transmission that returns an EPA estimated 23-mpg in the city and 29-mpg on the highway. The top of the line 1999GMCSonoma4x4 Extended Cab , priced at $ 20,079 , is powered by a 4.3L , 6 - cylinder engine mated to a manual transmission that returns an EPA estimated 17-mpg in the city and 22-mpg on the highway.