I am strongly leaning toward a GV behind my K20 for similar reasons - would prefer to keep the motor and t-case in the stock location, but the tradeoff is more $. GV behind an NP205 is around $3K, whereas a stout 700R4 could be a little less. Unless, of course, I forget and leave it engaged when in 4WD, then it just got a LOT more expensive
. Anyway, it's personal preference.
My gut reaction was same as kwmech, i.e. 3.54 might lug the motor if in O/D below 55 mph or so. It's easier to see the impact by looking at cruising rpm rather than final drive ratio. Here's a comparison with a 30" tire of your current configuration, adding a GV, and a GV with 3.73s. ~100 rpm less at 55 mph (i.e. the 3.54 with GV vs 3.73 with GV comparison) might not sound like much, but when it's ~100 rpm less from 1790 rpm, you start to get in that gray area where you might lug the engine at lower highway speeds.
To be honest, a 3.54 is a pretty user friendly highway gear - a GV price is a fairly high one to pay when you're not already revving to the moon at 65 mph anyway. But I do understand - I want one pretty bad too (but I have 4.10s
)
Also, to your comment about being sluggish in lower gears - it won't have any effect. 1st, 2nd, 3rd final drives all remain the same and you simply add a 4th o/d gear - unless you use it as a gear splitter to insert the .78 after each speed (i.e. operate as a 6 speed) - but even that doesn't affect your 'from a dead stop' performance, 1st is still 2.48 x 3.54 for a final drive of 8.78.