Your forend will fit both barrels fine and it will match your stock so I say stay with it, there are no drawbacks to using one forend on a couple of barrels. The Brennekes may still shoot great from your gun so for the $2.00 to $4.00 for them for a box of 5 I say definitely try them. For a only a couple of bucks a box I also suggest you try the Remington sluggers and some Winchesters and Federals, the Hornadys would also be a good bet. If you don't mind spending cash you might want to try the Remington Buckhammers but they are not any better than the Brennekes as far as knock down power and much more expensive, as a matter of fact the jury is still out on if they work better in Rifled barrels or smoothboes, I do not think they are particularly good in smoothbores. The modified choke will be great for shooting slugs...The Tracker 1 barrels are wonderful for slugs out to about 75 yards and perhaps a bit more as well depending on how yours likes a particular brand of slug.....<><....
P.S. - VERY IMPORTANT!!!...I suggest you only buy and use 2 3/4" slugs, unless you are hunting elephants or dinosaurs. I prefer 2 3/4" standard slugs over 2 3/4" magnum slug loadings. I and others have found they group better, are usually cheaper, and the recoil is less punishing. I am not recoil shy and although it doesn't bother me why take it if all you get is less accuracy, for more money, and wasted energy you do not need. There are some who suffer from that dreaded malady I call "Magnumitis" that will tell you bigger and badder is always better, do not believe it. Any deer hit in the proper place with a 12, 16, or 20 gauge 2 3/4" slug is "meat on the pole" in any deer camp....<><....
