[ossiblue]

What we may be seeing here is the difference between early factory installed radios, and those installed after delivery, by dealers. Possibly, some cars were sent to the dealer without radios, and the hole was covered by a plate that was then hidden by the dash vinyl. At the dealer, the plate was either replaced with a three hole adapter or the plate was removed and the radio installed with the face plate which laid atop the vinyl. If the radio was installed by the factory, then it came with the external face plate. This is all speculation and my scenario may actually be reversed, but it seems there must be some part available that adapts the opening to the look you want. What you need is for someone with a 71 that has a three hole opening to pull back the vinyl and see what is there (good luck with that.)