Modular counterframe, joinable to the frame of a truck to be fitted out for transport of an interchangeable body, said counterframe being anchorable to said interchangeable body and including: - a pair of side members (25, 26) each having at least one longitudinal groove along the entire length of a first side; - at least one cross member (27, 63) joinable, orthogonally, to the two side members (25, 26); - means (32, 33) for joining the frame to the side members (25, 26); - means (7, 8) for anchoring said interchangeable body to the side members (25, 26); - means (32v, 8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8) to the side members (25, 26), said means (32v, 8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8) being able to translate in said groove without transversal departure therefrom, positioning themselves at said joining means (32, 33) and at said anchoring means (7, 8), said counterframe being characterized in that said joining means comprise first drilled plates fixable to said frame and to be coupled to said means for fixing said joining means (32, 33) and said anchoring means (7, 8), said anchoring means comprising second drilled plates (7, 33) to be coupled to said means (8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8), said means (32v, 8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8) being screws and nuts, the screw head (51, 51a) having a prismatic profile that allows it to translate in said groove but not to rotate to allow the nut to be tightened, said counterframe furthermore including: - first hydraulic means constrained to some second plates for raising from the counterframe and lowering on the counterframe said interchangeable body while maintaining its horizontal position; - second hydraulic means fixed to said cross member by means of fixing means (11a, 12, 12a), said second hydraulic means being able to activate a mechanism (13, 14) for moving said interchangeable body lengthwise the side members (25, 26), in either a direction or the opposite one, to fix said interchangeable body to said anchoring means (7, 8). - a pair of side members (25, 26) each having at least one longitudinal groove along the entire length of a first side; - at least one cross member (27, 63) joinable, orthogonally, to the two side members (25, 26); - means (32, 33) for joining the frame to the side members (25, 26); - means (7, 8) for anchoring said interchangeable body to the side members (25, 26); - means (32v, 8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8) to the side members (25, 26), said means (32v, 8v, 33v) for fixing said joining means (32, 33) and said anchoring means (7, 8) being able to translate in said groove without transversal departure therefrom, positioning themselves at said joining means (32, 33) and at said anchoring means (7, 8), - first hydraulic means constrained to some second plates for raising from the counterframe and lowering on the counterframe said interchangeable body while maintaining its horizontal position; - second hydraulic means fixed to said cross member by means of fixing means (11a, 12, 12a), said second hydraulic means being able to activate a mechanism (13, 14) for moving said interchangeable body lengthwise the side members (25, 26), in either a direction or the opposite one, to fix said interchangeable body to said anchoring means (7, 8).