It all depends on what tires you want to run and how the truck will be used.
You hear people talk all the time about how much better OD is, but high gears with a 465 can pretty much match it. The 465 has a super low first gear so you will have no trouble starting with pretty much any tire/gear combo. The 1:1 4th gear isn't necessarily that low, especially if you have larger than stock tires.
What I'm getting at is on the street, with high gears (numerically low, like 3.08) you may be able to get good mileage for a K5. Remember that a manual is significantly more efficient than an automatic transmission.
The place where big tires and high gears (with a 4 speed) will really hurt you is offroad, and as I said the 465/208 combo is great for that. The 208 is geared 33.2% lower than the 205. Your potential 3.08's with a 465/208 combo are apprx. the same as a 465/205 with 4.10's. If you ever re-gear then the extra low range from the 208 will always be that much lower.
Of course, this all depends on the tire size you want to run and how much street/off-road time the truck sees.