Help w/ Model 30 Series and barrel type designations

I have a 12ga Model 30F Type 3 shotgun that I received for Christmas around 1975 or 1976 and I would like to get a shortened barrel for home defense. I want to be able to swap out the 28" Ribbed barrel that is for hunting or trap with an 18-18.5" barrel for home defense. Are these other series and designations ok for use on my shotgun?

Yes, most of the series designation letters have to do with small internal parts and stock variations.

Thanks! just debating with buying a used barrel for $100 or so and cutting it down to a 18.5" (just to be sure there isn't a problem) in lieu of buying a inexpensive shotgun like a Savage/Stevens 350 for a $100 bucks more........