That first one looks like a 4700 or 4900, they replaced the 1700 and 1900, I think in the early 90s, and you can probably find one in decent shape cheap. Most likely will have a DT466 and a Spicer 5+2 in it. Hard to kill them. A DT466 with an Allison auto is a nice combination.
Something like a Freightliner FL70 or FL120 would be a good choice, too. Or a factory or factory converted Century class daycab, but the converted one will probably be a long wheelbase tandem. The factory conversion has a very spacious cab.
GM used to make a good medium and heavy-duty truck, I don't know how the quality was on the later ones though.
Basically look for one that hasn't rusted away.
Pulling a gooseneck with a semi is nice. They are slower when you have to make a lot of turns, but you hit the brakes, and you STOP!