SBE I / SBE II design?

[Duckin]

So, Benelli’s fully rifled slug barrel which was originally made for the SBE will fit the SBE II.

 

With that in mind I compared my SBE to an SBE II.

 

It seem that the receiver is the same in both, as is suggested by the slug barrel fitting both.

 

So I am guessing that Benelli redesigned the trigger guard, barrel, forearm, etc.. but kept the old receiver. If this were true one could modify a SBE into an SBE II if one had the relevant parts?

 

I realize that this would not be cost effective as a new SBE II is probably cheaper than all mentioned parts but would like to know if this is correct.