There are several Drag specific tuning threads that folks have posted in the previous FMs Tuning Garage sections (ex. FM4, 5 and 6) which you should be able to search.
 Just go to the Free Play area, select Drag as the racing option, the tracks with drag capability will show on screen, then you can pick a specific type/environment (1/4, 1/2, 1-mile for 2 or more cars). Most of it is open, yet, you can be class specific as well (unless it was removed for FM6). I usually run R or P. I do have a 1968 Alpha Romeo 33 Stradale (P903-class, AWD) shared if you want to try it out. Also pulling one together for R855-class, RWD.
Try finding forza or drag specific clubs to join. Private lobbies are where you’ll find most serious drag racers and tuners. A private lobby like this usually will have vehicle restrictions Ex: 800 hp or less & 2800 lb’s or more. Shoot me a message online ill invite you to some clubs. GT: mxblaster292