Well I am wondering if the 70-72 Sportwagons where optioned with a 455 Engine? The older sportwagons/skywagons where available with the 400. Tim
Just to add a little texture to the history. When the A-body wagons had the 400cid engine, they were part of the "SportWagon 400" package in '68 & '69. At this same time, Buick only made one wagon model (line) in the A-body (as Buick did not offer a full-size wagon from the mid-'60's through '69). So, Buick, while offering the Special Deluxe Wagon (low price), SportWagon (mid-level) and SportWagon 400 (upper level), Buick essentially had all its "eggs in one basket" in that there was no dual channel for wagons adding a full-size wagon model larger than the A-body. Thus, Buick widened the offerings of powertrains and options with in the A-body model line to (try to) cover customer needs 'in '68 & '69. In '70, Buick re-introduced the full-size wagon (Estate Wagon) on the large car chassis with std. 455 engine. As the 400 engine was retired for '70 (replaced by the 455), the SportWagon with a 455 would have overlapped significantly into the Estate Wagon's "territory" and scavenged sales from that model. So, for '70 through '72, the SportWagon lost the upper level options and styling treatments from the earlier couple of years, namely the (Olds) vista-style roof and the availability of the big block power. This reasoning for these changes and restrictions were solely in the discretion of each Division at GM, because, I believe, over at Olds, the 455 was indeed available in the Olds line A-body for one or more years within the '70 through '72 models with the Vista Cruiser (roof windows and raised roof section), even though there was a full-size Olds wagon available at the same time. Simply put, Olds viewed the same situation completely differently.
