Sometime next week, weather permitting, I plan to photograph and maybe even try to ride an M3 set before they retire. Preferably, I would like to ride the Main Line but as far east as Mineola. Which trains do the M3s typically operate on during the rush hour?
They will be around for awhile still. You don’t have to rush to be on an M3.
M3s are used on more dense non double decker diesel routes since they hold more seating. Some lines like Oyster Bay use the double decker trains which are used at Mineola for instance.
Can’t answer as to how to make sure you are on an M3 trainset. I have been on M3, M7 and C3 trains. I presume I may have been on an M1 but I didn’t recall or check if it was an M1 or M3 at that time.