I would say it depends on what you use the car for. If you travel out of town to car shows or go on cruises you might not like the 3:91 gear. My Buddy has 3:91's in his BOSS and I know he'd rather have the 3:50's mine has.
I have 3.70's and a fmx, ok my car has 3.70's and a fmx and it turns about 3000 rpm @ 60 mph. If a OD is in your future go for it. I'd think about installing a tremec or something and have your gears. Changing your tire hieght will only change your effective gear ratio back some, no advantage.
Well, again I'll be the spoiler(pun intended) I have taken my '70 Spoiler on parts of the Power Tour. It's a 4:30 Drag-Pak car. With a 25" tier I can still run 65-70... it twists a little but I still get around 17 MPG. It pays to tune the hell out of one at the strip! Car has a little over 50K on it & it loves the 4:30's... so does the loose nut behind the wheel. Ask everyone's opinion, listen to them all no matter what... & draw your own conclusion.