Need Starter help!

[frsyth72]

Well here is the story, a couple months ago my starter went out on my 72 blazer (350/350/205). Anyways I put a new (reman.) starter on and it ran good for about a month then it started grinding really bad then cought on fire, big cloud of smoke and that great burnt electriacl smell. I got a new starter and put it on again it ran good for about three weeks and started grinding. We noticed that the flywheel had gotten chewed up from the grinding and threw a new flywheel on with and warrentied out the starter again. it started grinding really bad fron the start. we started really playing this the clearances with this new starter (Before I only needed on shim for the alignment of the other starters) but with this new one we had to stack up 5 shims on the outboard bolt to get the clearance right but it would still grind when we went to start it now I have put in a couple Chevy starters before and have never had any problems like this and have had three other people look at it with me. Can someone please offer any advise on what I might be doing wrong or what the problem might be. Oh and we where using the gauge that came with the shims to check the clearances. Thank you in advance for any help you can give, I am lost.