I'd say if you make a deal on a 71' auger, be sure to ask and get it in writing if you want as well, that once it gets on the yard and you discover its not going to work ( it probably will but probably is no guarantee ! ) that you can exchange it at no penalty with a model that will reach.
Keep in mind that just because an auger can physically stand on its end and squeak in to fit, depending on the auger boot style at the main auger, it may not be able to take what the swing auger can gulp up and end up with grain puking out of the relief door or a sheer pin going etc. We have an older spray aire 10" x 60 auger and it is not a joy to fill bins that are 30/31' high just for that reason alone and as they are only 14' bins, the main wheels fit fine but I wouldn't want any higher bins for a 60' auger then this. Thankfully we don't have to use it anymore as we have a 70 and 91 foot 13" to do the bin filling.
I have no clue what your yard layout is but for ourselves we have some bins in one row set up long ago and they are hoppers on cement but only small 14" bins sadly, in this case its far easier to line up with the truck to the 91 foot auger because I can be so crunched up with the auger to the row of bins with that insane reach it has for the height and diameter of them. So I don't have to bother backing up a truck/trailer, I just drive by the nose of the tractor and swing the auger under the trailer. There is no rule book that says the tractor/trailer has to be lined up beside the main auger parallel, the tractor on the other hand should always be straight with the main auger tube because of driveline issues.