Not sure about that one. Who covers Russ Francis?
The 84 49ers could very well wear down the Patriots front seven with Roger Craig AND Wendell Tyler (who was an All-Pro that year, lots of sets with both of them in the backfield), and take shots over the top on that average secondary. Lots of Dwight Clark (at 6'4") on Ellis Hobbs (5'7" on a tall day).
They wouldn't generate much of a pass rush (Fred Dean the only one who would need gameplanning for), but did have Ronnie Lott at safety.
I think the 49ers could ball control the Patriots, 2/1 TOP kinda stuff, and keep it close if not outright win.
Certainly not 'clearly have beat' like the 85 Bears (07 Patriots might win that one by 30) or the 91 Redskins (another very favorable matchup for the 07 Patriots).