Carl,
It looks like Saturn and Ford engineers have said the same thing about the space saver wheels being the same strength as normal road going wheels. I guess the Ford engineer actually does know what he is doing. :=d
I'll bet the rim is stamped with the DOT numbers also, indicating they are made and tested to specific standards. (mine were/are)
I think your plans to use these wheels is just fine. Actually having Taylor put in solid 5/16" centers and insuring latteral runnout by stamping, or "coining" as production wheel manufacturers do is good insurance. My lakester and Liner wheels were made by Hoppy Hopkins, and needed a bit of straightening after welding. After making my latest wheels he indicated that he is retiring from the race wheel business. I have not talked to him for a number of years though.
Good luck with your project.
Rick