There are 2 starters for your engine and the small block V8 of similar years. One is for the 153 tooth flywheel and one is for the 168 tooth flywheel. Tech specs will indicate a variation in starter rpm and ampereage draw from different starter part numbers but for the Inline you can use almost any of them with sucess as long as it meshes with your flywheel.
As far as the support bracket being off the front cover or off the top of the case, you are correct.
I have run both the Inline and V8 engines without the support bracket with no problems. The shop manuals and others will tell you the starter will break its aluminum nose if you don't install the support bracket. I've never had that happen - yet - and have had them on an engine for 60,000 miles and more with no problem.
So I would say if you can't find the starter with the threaded hole on the top of the case, don't panic. You'd be surprised just how many are out there without the bracket. I bet if the parts guy took the time to open all his Chevy starter boxes he'd find one with a hole in the case for the bracket, even though his parts listing only shows one part number for both the Inline and the V engines.
