I have a "built" 396 stroked Windsor with an aggressive cam, and the .68 fifth in my Tremec 3550, pushing a 3.73 rear. I cruise at 60 mph at 1900 rpm, easy and relaxed. i can putter around town in fifth at 1000 rpm without any shudder or shake, and even accelerate without protest in fifth. I like the tall first, as i never have to slip the clutch a bit at a start. I upshift out of forth at 6K rpm at about 130 mph on the track. For my driving, this is perfect. I have driven another SPF with the .82 rear in front of a 3.08 rear, his gears are more "long-legged" than mine, we are pulling the same rpm at cruise, too. But you have to slip his clutch a tad from a stop. He likes his road gearing, i prefer mine.
I think a lot depends on your cam and heads, and how slow an rpm you can run your engine with reasonable drivability. If you want to play with gearing, you can pull up Mike Stenhouse's gearing comparison on the Second Strike web page.
try
www.secondstrike.com and plug in your choices