Rob Ryan didn't install the 3-4 in Dallas. It had been in place long before he got there via Wade Phillips. The reason Ryans defense regressed against the run can be attributed to losing Sean Lee, Bruce Carter and Jay Ratliff for most of 2012. The improvement in the secondary and passing defense came via adding Brandon Carr and Morris Claiborne.

Take any defense and remove the top 3 players versus the rush and add two top tier secondary players and you will see the same result. This is absolutely nothing to do with Rob Ryan.

I have no issue with Grantham as a candidate although his defense also regressed much the way Ryan's did in Oakland. I think he would require surrounding himself with positional coaches with more NFL experience to avoid tripfalls, but I don't see the relevance of the 3-4 installation arguement. If that is the case, Crennell is the clear cut best candidate.

He installed his own "version".... Did not continue with Wade Phillips 3-4...

So yes, he installed a 3-4.

One of the pleasures of Cowboys camp is watching Rob Ryan install his version of the 3-4. It's a far more motion-based version, compared to Wade Phillips'. Thus far, Ryan has stuck to the templates he established in Cleveland. Look for base 3-4s on early downs. When Ryan gets an offense into passing situations, or when he's facing a spread offense that used three or more receivers as a base, look for Ryan to go ''psycho.''
Dallas Cowboys News & Analysis | Cowboys Nation: Rob Ryan -- Psycho Like a Fox?

He installed his own "version".... Did not continue with Wade Phillips 3-4...

So yes, he installed a 3-4.

Installing a 3-4 on a 3-4 and installing a 3-4 on a 4-3 are two vastly different concepts. He's putting a 427 in a 396 car. The other is putting a Ford engine in a chevy. The semantics of your link are just that. He's adding wrinkles to a base scheme. Not completely changing overall front 7 personnel formations and gap responsibilities. He was working with guys who experienced a 3-4 and not trying to fit square pegs in round holes like he will be doing here. Absolutely any coach going to a new team is installing their own version of any base defense. I do not credit Spags with installing a 4-3 when he came here last year. We already were a 4-3 but under a different coverage and pressure concept. Certain responsibilities change and that's it.

Fairly moot point to argue as I am not an advocate for Ryan.... So thanks for proving my point... Grantham > Ryan