I am not 100% certain this will work because I have not tested it yet, however, I recently noticed the brackets at the bottom of a door that hold the window stop bumper appear to be identical to the seat brackets, except they lack the extra tabs that make the seat ones easier to weld to the floor.

To my knowledge nobody reproduces the seat brackets, but if you can find a couple of rotten doors to rob the brackets from, this might solve your problem. Let me know if my theory is sound.

I have posted pics of actual seat brackets below with the tabs. I can't seem to find my loose door bracket that made me draw this conclusion, but other than the tabs, I swear they are the same. It does not show the bracket measurments in question, but third photo shows locations of everything else. I found it a while ago in a search I did. Hope this helps.

looks to me like the seat bracket would be approx. 3" from the wheel well edge is that about right? It does not specify the exact location of that bracket. Could anyone confirm that?
Thanks

Thanks London Steve. I made a set of brackets out of heavy sheet metal and when lining everything up I found the same as you that there is little room from the lower panel. I still have to finish them and I will try and take pictures of them when done for others. I will include the measurements. It is not hard but it is a bit time consuming. I also found an old door and unfortunately the bracket spoke about earlier in the post is not correct. Would it work? Maybe but would take almost as much modifications as just making them. It is heavier metal which would be a plus but I really don't think it is needed. Anyway thanks for taking the time and I will verify my measurements with yours to see how close I am.