Simon, Simon.....haven't you been reading all the posts in GT forum and restoration forum on this very topic? I thought that's what the moderators spend all their time doing?.....just kidding. I'm not the expert on this topic (Akitaman is and will probably chime in here) but I have seen in real life various supplier's floor pans and I will list them in order of least to best (at least from the ones I've seen to date).
Wolf Steel....avoid like the plague IMHO, the extra work to weld up all the open joints is not worth the savings and they will not look like the original Alfa pieces by any means....contours are 50% accurate (if at all).
Parts from Classic Alfa and Alfaholics (I've purchase a set of these from each, see link below) will undoubtedly be some of the best w.r.t. having the correct crisp contours and definition in the right places...I'm very happy with them even though some were missing the reinforcing doublers in the seat mount areas. I would wager that the other suppliers like EB Spares, Highwoodalfa, Alfa-Service and OK Parts are equal to these as well. I don't know what the US suppliers pans are like so I can't comment on these.
AFrench Blue '69 GTV Restoration
Now the best ones that I've seen so far are the full length floors from Biondilamierati (Italy) since they had all the reinforcing doublers for the seat mounts and were of superb workmanship. the only issue is arranging for the shipping and paperwork. (Luckily it looks like you won't need these anyways).
One last suggestion....if in doubt about what the supplier is offering, ask if they can send you a photo of the item first. This is what I did with Classic Alfa and they promptly did just that.