Based on the position of the outside edge of the front tires with the 3" fender extensions, I'd say its an early (88-96) Dakota chassis (looks to have 5 bolt wheels, without the fender extensions, the Dakota chassis puts the outside edge of the tires about even with the fender lip) . An S10 chassis would have the front tires nearly out of site with the fender extensions (the tires usually sit inside the fenders a good 4" without the fender extensions). The truck sits pretty low to have the original beam front axle with the big block sitting where it is (the oil pan sump would be in about the same position as the axle.

At least that's my guess based on having built a couple of this era Dodge trucks. Gene