I'll take a stab at what a "perfect" 3-4 line up would be.
NG- Run stuffer extrodinaire. Must be able to get a puch up the middle on passing downs. Think Quinton Echols
SDE- Must be strong against the run and the pass. Put your best Dlineman here. Think Adam Carriker.
WDE- Can maybe afford to be a little smaller and faster, usually can have the outside edge on a OT. Think Ian Cambell
SOLB- Have to play the flat and cover a RB in pass coverage, jam the TE on the run, and be a pass rusher off the edge. = Josh Buhl
SMLB- Again, up the middle is big in the D, so he's got to be great on run D. If he can blitz, perfect. = Thaddeus Washington
WMLB- very similar to SMLB, but is generally going to blitz more often. = Rufus Alexander
WOLB- Fastest LB of the bunch, will blitz, play coverage on some slot recievers. = Terrell Farley, perhaps?
That would give me a dang good front 7.