the first link: i'd get a hell of a lot more info first. for a "professionally built" engine it looks like crap. at best it's been sitting for a few years and you'll have to pull it apart and de-rust it. and it's a solid roller with a single plane intake. i'll bet the street manners suck. you'd have to constantly adjust the rockers, and the low end power (since solid lifters are usually for a very big cam) will be non existent.
the last link: again, more info needed. when was it pulled, where was it stored. if it's been sitting for a year w/out a cover--lots of rust, maybe water in the oil killing the bearing surfaces. but, i'd rather go with this one. pull it apart, clean it and do a basic rebuild plus a new cam, intake and carb. remember, a 73 truck would be emissions and very low HP. the intakes were restrictive, cam's small (good torque though), and the heads anemic. i probably do this even if it got pulled yesterday--unless they can demonstrate that it's in great shape.
it also depends on what you want--strip, street, basic cruiser, lowrider, show car...