To quote the factory literature on the lockup changes, "the case was revised to provide clearance with lockup valve body." So the case was (is) an issue. The pic below shows the point of major interference between the lockup VB and the non-lockup case.

Your initial reply to the OP stated "You can turn a non-lockup trans in to a lock up - need the valve body, input shaft and corresponding rear clutch retainer, pump support (reaction shaft support)." which implies that the case is OK as is. Whether the revision is in the casting or "machining" it's obvious from the pic and the factory literature that it is an issue.