At it's simplest, a 3-4 and 4-3 are the same thing. The only difference is one of the DEs is standing up and playing LB. The issue is the offense does not know which LB is playing DE. It presents lots of options for blitz packages. You can overload the blitz on one side sending the ROLB and RILB. You can send the ILBs on inside stunts with the NT and with each other. It's vital that the RBs are ready to go with pass protection. If a side is overloaded, they'll be responsible for LBs that get through the line freely.
Different play calls? I don't know if you call too much differently. You do want to get the team out of their blitzes. That can be done by throwing quick passes, draws, screens and in general a solid running game. The option also works. If you blitz to the QB, the RB gets the ball. If you run blitz the RB, the QB keeps it the other way. I'm not sure if that's different than a team running a 4-3. You want to get them out of their blitzes too.
The one thing you will see is that 3-4 teams are typically bigger across the front. That's because there are 3 of them and they often lineup over the C and OTs rather than outside the OT and between the OG and C. I would expect a college DT to be 285 minimum. I would want an NT to be 300+. I want my DEs to be 260+ in a 4-3, but 280+ in a 3-4. You need bigger guys to eat up more blocks since there are 3 of them. In 2012, Notre Dame ran the 3-4 very well. DT Louis Nix is 330 lbs DE Stephon Tuitt is 300 DE Kapron Lewis Moore is 315 and DE Sheldon day is 290. These are big boys. The lineman I'm seeing starting for Stanford are in the 270-280 range. That's ok for the DEs, but a 278 NT is pretty small. Their big guy from last year David Perry is with the Colts.