Wow, 300K is getting up there, even for an 80 series. I would make sure the head gasket isn't leaking, that's a common problem. Also check the diff fluids fro signs of axle grease and the hubs for diff oil. With that mileage, the axle seals will have likely worn a groove in the half-shafts and allowed the heavy axle grease and lighter gear oil to mix. The fix involves new axle shafts and axles seals.
The '97 is promising, but you will need to budget for an aftermarket bumper. I suspect it was crashed since the bumper is missing, the hood doesn't match, the grill isn't fitting properly and was rattle-canned, the headlights and turn signals are eBay Chinesium junk, and it just had a radiator put in. I would inspect it for hidden damage. Also, who does all that and still didn't notice that it is an inline 6 and not a V6? It may be a clean title because the wreck was done in the back yard and never reported to insurance.
That last one I would avoid. Smoking from the engine? I bet the guy got it on a whim and realized there is something seriously wrong that he doesn't want to sink money into. Judging by that monstrosity of a bumper, someone probably was screwing around and didn't know what they were doing.
