Those early Tempest had rear swing axles like the early Corvair. The car in the article has a 389 that looks like it was born there, plus a solid rear axle that just happens to be a 9" with 4.56:1 gearing. That thing is probably pretty light, and being a wagon will carry a greater percentage of the weight rearward.   It could probably carry it's front wheels off the starting line, too!

A friend with a '62 Olds F85 pointed out to me an interesting fact, that the Tempest, F85 & Special all share the same doors, body style for body style. Yet all the models come out looking different. They also shared more body structure with the Corvair. GM designers were pretty sharp and on a roll back then.