While top loader is certainly the 'correct' way to go a five speed can be pretty nice. For me the 'key' would be MUST have a 'correct' style gear shift, forward swept like the top loaders have. Not sure you can do that with a five speed.
HUGE down side of the five speed, as noted above, 1st and 2nd gear are basically useless. Combined with the typical .6 overdrive which WILL 'lug' the engine without a really low rear gear (and that further complicates the 1\2 shift points) and the overall package just doesn't work well at all.
What to do? Get a five speed that YOU can specify ALL the gear ratios for. You want a 1st and 2nd gear that is as close to the top loader ranges as possible (the WIDE ratio top loader, not the CLOSE ratio top loader, big difference). Then go with a .8 overdrive (thats a MUST have in my opinion). Run a 3.5 rear gear with this setup and you will have the 'perfect' trans solution. Now this ASSUMES you can get a 'correct' style gear shift (and put a four speed knob on it)!
Oh, and do go with an FE block of some kind, so you'll be 'different'!
