I think there is a common misconception that the 4-3 is the better run defense. The 3-4 typically is. Gross generalizations to follow: While you have fewer linemen in a 3-4, all of them are 300 pounders. In a 4-3, only your tackles are over 300. Add in your outside linebackers and a 3-4 becomes a 5-2 on running plays.
As far as 'real ends' on our roster, we don't have any. Worthy, Daniels, and Neal are 3-technique tackles in a 4-3 scheme. The closest thing to a 4-3 end we have on our roster is Perry. Actually, Perry would likely be a more impactfuly player today as a 4-3 end. To a lesser extend Matthews might work as a 4-3 end, but he's about 10-20 pounds light to do it every down.
To put this in different perspective, look at our nickel defense. We trot out, from left to right, Perry, Neal, Raji, and Matthews. Have Perry and Matthews put their hand in the dirt. Ta-da, that's our starting line if we switched to the 4-3 without a huge influx of different body types.
To really make a go of a 4-3, we'd need another stud pass rushing end to pair with Perry. Matthews would probably become our strong side OLB and Hawk and Bishop as the Middle and Weakside backers. Who is who would depend on the specific scheme. In the Bob Sanders/Jimmy Johnson scheme, I'd probably put Bishop in the middle as that is the play-making position. In most others, the weak side get the glory and more coverage responsibilities, so I'd put Bishop there. Not that he's a great cover man, but better than Hawk. Really, we'd need another play-making guy to replace Hawk, but if we're doing that, let's just get him anyway and stick with the 3-4.