Game has changed since 98. However, Salem in 98 very very physical, big and fast. No team mentioned would have been as big. No team would have been more physical. They also had speed at the corners and linebackers (and yes I have seen in person or on tape all teams mentioned). Remember this, Salem gave up 64 points that year in 14 games. They were not as high scoring as recent teams but that was because of the style the played. Depth was also not a problem, one player went both ways (slot receiver outside linebacker).
Ok, An article written in 1998 says that Salems line averaged 265 (big yes), but Phoebus line averaged 270 and I would surely say they were just as physical as the Spartans. No way in hell they were faster than Phoebus. No one, could run on Phoebus. Hell, Adam Morgan (Dinwiddie) broke state records with 3216 passing, 716 rushing 4032 total yards 39 tds in 2008 and Phoebus crushed them 37-13.
Here is the kicker. You said Salem gave up 64 points in 14 games (nice). Phoebus gave up 53 in 15 games, beat 7 of the top ten (they were #1) teams in D5 (Hampton, Warwick, Bethel, Green Run, LT, Stonebridge, and Dinwiddie) and more importantly scored 720 points (nicer).
Cut the cake anyway you like. No one can touch those stats and no one has ever beat that many good teams in a season. Salem 1998 was a great team, but their schedule doesnt even remotely come close to the Phantoms.
Still cant prove it, but I saw Salem 1998, Hampton, Phoebus 2008, 2009, 2010, live brother and they would not have won. For what its worth your announcer Three Putt (homer right?) says Hampton with Curry was the best high school team ever.