I am willing to bet the 330 Pete has had most of its 100k miles doing short runs, probably off road or out in the oil fields moving equipment. The steel Dayton type wheels are typical for off road, and construction type trucks, (very heavy, hard to balance, and a PIA for most situations. Most all highway rigs will use the more common Budd wheels. Going to be a rough riding truck and the engine will turn too many RPM at any kind of speed with that gearing. The 3126 in this truck and the C7 in the second one are almost the same engine, the C7 has different heads, software, and emissions. These engines are designed with a RPM range of 1800 to 2400, with best fuel economy at 2,000 RPM. On the other had, it will do a good job of pulling stumps out of the ground..lol. In this market there a lot of highway rigs out there for a reasonable price, check commercial truck trader, or Truckpaper.com.
The second truck looks like a pretty good deal at first glance. It was specified with 100 percent class A driving (highway-on road) has a much more reasonable 3.90 gear ratio. it does have a 10 speed direct transmission (no overdrive) as its primary use would have been city driving with not much high speed. depending on your driving habits, (mountains, speed, weight) a change of gears or tranny swap might be in order. Lots to think about if going to convert the existing box. There are three sets of double doors to be removed (unless you need a garage) and skin over. One could add a false floor and or false ceiling to conceal plumbing /tanks/ducting etc. Might be able to extend the side skirts down and make some basement storage. going to have some fun cutting a hole thru the back of the cab and into the box. I do see lots of potential though. looks like a well cared for and documented rig. and no quick detail/cover ups from a dealer.
The whole topic of buying ready made and building your own remains to be determined. I believe that most sane people will side with Blizz and find a great deal on a used one, which by the way I fully agree with (exceptions to be listed later..) and there are those who boldly choose to go ahead and build a creation of there very own (and yes Kenn I am talking about you, and not eluding to the fact that you may be not 100 percent sane, but you did run into burning buildings for a living). I have searched racing junk for several years, and have yet to find a rig is both affordable and meets my quirky needs, that and the fact that I believe that sanity is for normal people, means I will pretty much be building my own also. (strange I have also run into burning buildings...I see a pattern here..lol)
Most importantly no matter if you choose to buy, build, or remodel, do it because you want to, be proud of what you end up with, and I will support you all the way.