It would be easy to find the freq of that truck. Measure from the base of the windshield to the farthest back point inside the cab. Convert to feet and then divide that into 1130 (speed of sound in air). If too high, divide by 4 to find the quarter wave.
Ex. 105"/ 12" = 8.75ft. 1130/8.75 = 129.14 Hz. Since thats too high of a note divide by 4. 129.14Hz/4 = 32.28Hz.