Picked up an unused remanufactured starter for my SD and hooked it up to a 12 battery for testing and got nothing! It had been sitting in an garage, had some light rust but I would think that it should still be able to turnover outside of the car -any thoughts?

You should be able to rotate the starter shaft by hand. If you can't then it is probably seized mechanically. If you can but it doesn't rotate when connected (correctly) to a battery then it is shot electrically. Check the brushes to see if they are OK and the commutator to make sure it is reasonably clean. If they all check out, it is likely a winding problem.

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1991 M-B 560SEL Arctic White/Grey 99,000 Miles
1987 M-B 300SDL Ivory/Palomino 229,000 Miles (sold but never forgotten)
2006 Volvo XC70 Blue/Beige
1999 Porsche Boxster Arena Red/Savanna Beige
1986 Porsche 928S Goldweiss/Brown

All is well -used beefy jumper cables versus my neighbors test leads which were under cabled for the job -starter works great!