A 70s Sears ST 10 will also have the same one.
Here is one on ebay now, http://www.ebay.com/itm/SEARS-ST-SS...687?pt=LH_DefaultDomain_0&hash=item45ff5888c7 It says it needs a little work. Looks like part of the side is missing though. Dont know if it will help or not. Your right, the lower grill just bolts onto the frame. I believe the twin cylinder tractors were the only ones with the spacers under the grille.it looks like i found the answer to my own question. by googleing st10 i found some new to me pics that i hadn't seen yet. i knew the grills were different from the st16's and such, but as it turns out it seems that the rt10/st10 doesn't use a spacer or bracket between the frame and the lower grill at all. the cast for the grill incorporates mounting holes at the correct distance so it can be simply bolted to the frame. now the question is can i find a new proper one or make mine work some how. the busted off hinges on the top are giving me the most trouble. thanks guys