[Super Nove issues solved?]

I own an old Nova and 2 Supernovas

The old reported trigger issues are well known and the simple fix is to clean and oil well.

I never had an issue with the SuperNovas. 

[Rifled barrel for a 12g SuperNova]

Benelli sells it, hard to find one in stock.

Old Ithica barrels will also fit, I have one with a cantilever scope base. 

[Supernova issue]

I have 2 Supernovas and 1 Nova, that is normal.

All 3 of my guns have varying degrees of it. 

[SBE 3 Scope Question]

Weaver base number 93A or (48506) depending on the seller.

I have 2 bases for bird and slug barrels, work great.

[Super Nova Comfortech to Pistol grip]

I have Benelli factory one installed on my Supernova, I did not add any additional parts during install.

[Progressive Comfort Stock cutting?]

I took 1.5" off a steady grip stock as I'm  short guy, not hard to do with the right tools and mechanical ability.

Not sure that a comfort stock has enough extra material to allow material removal without effecting the anti-shock function.

Bring it to the gunsmith who can determine if it can be done.