Actually, this could potentially be one of those "grey-area" firearms - those imported post-89 "sporting purposes" importation change, but pre 11/90 (922(r)). Of course, in 1989 the type of firearms the ATF would approve for import changed, but once the rifle was in the country, it was not illegal to put it back into "evil" configuration until the passage of 922(r), which took effect in 11/90. In fact, Springfield sold a package (I believe they called it their "accurizing package) with both these guns and the SAR-8's that did just that.
If the rifle was put into "evil" configuration before 11/90, then it should be grandfathered and can have all the "evil" features you'd like. However, since you aren't the original owner, there really is no way you can tell for sure - then you get into the issues - whose has the burden of proof, etc.
Your best bet is to call Springfield - they can tell you when it was imported and when it was first sold. If it left their factory post 11/90, you are out of luck for sure... They may also be able to tell you if it was sold with the aforementioned "accurizing" package - which should be proof enough that the rifle would be grandfathered. Otherwise, if it left them in the "sanitized" configuration but pre 11/90, you are in the grey area...
Rocko