Chris,
You can only buy from Bar-Sto two ways: 'semi drop-in' or, 'custom fitted'. You certainly don't need a custom fit job on a Glock. They'll sell you a, 'semi-fit drop-in' that may not require any fitting at all. If the pistol goes together when you get your new barrel, try shooting it that way. After a couple of magazines take the pistol apart and see where the scuff marks are. It's your choice: Either lightly file them smooth and then polish, or just continue to shoot the new barrel in.
If the slide doesn't fit, hold it up to the light and see where. If the frame won't go on or the barrel rubs tight, again, use a magic marker and look for the scuff marks. (I very much doubt that this could, ever, happen.) Don't feel like doing any of the normal fitting? No problem! Bar-Sto is very reasonable on semi drop-in barrels. Send them the barrel and slide, along with $15.00 and they'll do the fitting for you. (Really shouldn't be necessary.)
You've got expensive taste, my friend! Then, again, there's a lot of good old fashioned, 'snob appeal' to the words, 'Bar-Sto' on your barrel. Everybody seems to spot it on my pistols!
Remember, you don't have to spend twice the money for a Bar-Sto when a Lone Wolf or Storm Lake will do. I do it because I've been using these barrels for more than 25 years; and, I absolutely swear by the low muzzle flash, much cleaner front sights, and reduced recoil of Bar-Sto's EDM muzzle ports. (None of the usual problems you hear about with SLIDE porting.)
Here, see what I mean. This is after 100 rounds of filthy dirty Winchester, 'White Box'!