My son is only 12, although he needs a 140...
My son is only 12, although he needs a 140 board his feet are adult size men's 8 will putting bindings on this board to accomodat ethose boots work?
How tall is he? How much does he weigh? Are you sure a 140 is what he needs? If he is 80 lbs or more, a 145 may work. And if he can go up to a 145, he could get a wide board- which would certainly work best.
I am not 100% sure, but I think that an adult small binding would fit on a 140. A medium MAY also work...depending on how the angles are set.
The board will fit any bindings you need to put on there. If you son is a size 8 in men's then I think you may want to get the 145, it all depends on his weight though. If you put a mens medium or small on this board it will work just fine, don't worry about it all.