It's not nearly the same, but in my '33 coupe I looked at the TKO 500, but with my engine putting out 475 foot pounds of torque I opted for the TKO 600 for a bit more cushion. My car's light, but I felt better not being right up against the torque rating. I went with a single disk clutch and haven't seen any issues.
On your cruise (curse) efficiency, it's going to depend a lot on your torque curve. I've got 4:10 rear gears too, and my cruise is 1995 at 70mph in 5th on 31" tall tires. My torque curve climbs steep from the idle range, rolling over and staying almost flat from 2000 out to 6000rpm, so the OD ratio is a great fit for me.
My first gear is very short, and I'm not near quick enough for a WOT launch in 1st, grabbing second before hitting the rev limiter. With the 4:10's and tall tires the acceleration is wicked, and the cruise is mellow. Like Mike said, I think you ought to look at the TKO 600 too.