The PMGR stands for permanent magnet gear reduction. I can't find anything on SD255. Doing some searching at Auto Zone and Advance Auto parts showed images that all looked the same, a typical Chevy starter. I would contact a local parts store see if they have one in stock. Pull your starter out bring it with you to match it up and have it tested. Most stores have a warranty on starters. Do you want to pay to ship a thirty pound starter back and wait two weeks for them to ship it back if you have a problem. Also remember that rebuilt is a relative term. Some people take it to mean they fixed what was broken, to someone else it means replace everything that could wear so it is as it was new. Buying on line may cost less but be sure you know what you are getting.