Remington Tactical chokes

[coppery]

I'm buying a boat...I mean a bare bones 870P. I want to add the same brake my old shotgun had which is the the ported choke with the spikes. So here is my problem.

There are TWO OF THEM. I do not remember which one comes, or came(8 years ago) with the 870 Express Tactical. Links below, but one has the threads up near the brake, and the other is at the end of the tube.
https://www.remington.com/shop/Rem%E...d-Only/p/19791
https://www.remington.com/shop/ProBo...d-Only/p/19792

The question I have is this: I know one IS cylinder bore, but do not know the outside tube diameter, and I know the others tube diameter to be ~.73 but do not know if it is JUST cylinder bore, and not improved cylinder.

I'm not trying to spend $100 do find out. Can anyone help?

What my ultimate goal is here, is that I want to have the barrel ported by vang comp, AND have the brake, along with back-boring, and lengthening the forcing cone. I saw a photo of that setup online, so I know it can be done. https://www.thefirearmblog.com/blog/...remington-870/
I'll find out the barrel thickness when I get the gun, but it would help to know the dimensional specifics of the two chokes to know which one I need since I want a cylinder bore, but also the best chance of having the vang comp ports as well(which would be the second brake linked since the threads are closer to the muzzle). Since I want to back-bore the barrel, it would be important to know the tube diameter to make sure we leave enough material for the threads, and make sure the wadding does not get hung up from the transition between the bore, and the choke.

This is all I found "Probore barrels are .735 in diameter, vs the .727-.729 of the regular rem-choke barrels. So a SLIGHT overbore.".