No brainer, go with the 06 KR. The 99 should give you 16-18 mpg, not sure why the guy was only getting 13 with it but be that as it may, thats what its getting so dont expect to buy it and get 18+ with it.
The 06 should give you a solid 15-18 mpg and over all is a much nicer (creature comfort wise) truck than the 99.
that's about all I could muster out of mine untill I put the chip on it.. a lot more fun and easier to live with getting an additional 125 miles on a tank..
anyway, I agree..
go the KingRanch. It will hold more value longer.