3 Down Linemen formations are as follows:
The difference between the Nickel-3-3-5 & the Nickel-Normal/Strong is that the Nickel-Normal/Strong have 4 Down linemen, 2Linebackers & 5DBs as compared to the 3-3-5 which has 3 Down linemen, 3 Linebackers & 5DBs. So the difference is that the 3-3-5 has an extra Linebacker in place of a Defensive tackle and vice versa. You can visually see the difference, just look at the D-line first, then work your way up.
Online SN (PS2) - BOLTPRIDESD
BOOBOO619SD - PS3 Gamer Tag