Is there any way that we could play both the 3-4 and the 4-3 to confuse the offense.
Yes and no (heh heh).
Seriously - for teams wishing to install either the 3-4 or 4-3 as their base defense, they need to configure their defensive roster so that the right kind of players tailored for DE, DT, NG, OLB, MLB and ILB.
For example, the 3-4 usually requires 2 very large DE "tree trunks" who can anchor plus a fireplug shaped NG in the middle. The two OLB's are usually Raynoch and Levar types either or both of whom can be brought on the pass rush.
The 4-3 usually employs a big LDE, a penetrating DT, a stay-at home DT and an speedy, smaller edge rusher at RDE. OLB's usually consist of an SLB who's strong at run support and an WLB who can blitz when called on.
But there is no reason why the Cards couldn't operate out of a base 4-3 and include one or more 3-4 packages if they have the personnel to do so (and I agree - we do). If nothing else, it could really disrupt an enemy offense if snuck in there at the right time.
I'd be willing to bet that many NFL teams do precisely that. (If many defenses are already using zone blitzes with guys at strange positions blitzing or dropping back into coverage), there's no reason why they wouldn't do some juggling of defensive personnel and shifting around to create a 3-4 look every once in a while. We TV watchers would be better able to see this if we could see the whole field rather than what the TV screen shows.