[Luce]

Late here to comment, but I have the same engine with 3.55 gear and T56, so same .63 or.64 6th as your OD.

Mine is perfectly happy (smooth) all the way down to 1600 RPM, but I don't like the lack of acceleration in that RPM range. I perfer to keep it above 1900. But for purring down the highway with less drone, it is very nice.

If i was to go with a 5 speed, I would choose the next lower rear (numerically higher, 3.27 is it?) and the .84 OD. The 5 speeds with the .64 OD feel like they're missing a gear, and the 427 in a Cobra makes 1st gear like a granny gear in a dump truck. Unless you plan on doing a lot of parades, it's worthless.