Nba guys in the NFL.

Tight End

Long snapper 

Tractor Traylor @ nose tackle.

There'd probably be three types of NFL players some NBA guys would fit into.

The Deion Sanders Category. Allen Iverson was the top FB player in the nation his senior year as a QB. Would have been a tremendous CB given the change of direction and quickness.  A lot of the point guards probably fall into a similar category (Isiah Thomas - the Pistons version being an obvious one).

The Cam Newton category. The shooting guards (or taller point guards) who were solidly built in the range of 6'3 to 6'6 would probably play QB (Oscar Robertson, Russell Westbrook, and many others). 

The Gronkowski types. A lot of the ripped 6'5 to 6'8 guys would have made great TEs or Des (Lebron James, Draymond Green, Charles Oakley, etc.). 

About half the NBA wouldn't be NFL prospects because of being too tall or too thin.  Once guys get above about 6'8" the height is a disadvantage (except on things like FG blocks). The long legs are too big a target for blockers. The skinny guys like Kevin Durant or Steph Curry would get broken in half eventually. 

The sturdier tall players in the NBA don't have to have good hands.  Need speed to stay with the receiver and shift to tip it.