Plus since you don't want to cut or modify your floor, that pretty much kills all of your 5 speed options, other than Jamie's unit, because my understanding of it is that he got it all to fit inside a standard 4-spd box.

with a big block and not wanting to do any metal modification, then your 5-spd options are going to be extremely limited.

The gear vendors are nice from what I hear, I've never used one myself...but they are also not cheap, and their OD is only a .78:1

What's the OD ratio in the passion unit? the TKO has a .82 or a .64OD. that .64 allowed me to turn only 2400 rpm on the highway with 29" tires, and 4.56 gears in the axle.

for reference, my current truck had an NV3500, with a .73 OD and with 26.7" tires, 3.92 gears, I was turning nearly 3,000 rpm at 70mph