I had a mechanical pump on my original 77 with all the factory mounts, etc. I don't recall if it was a specific model pump, or if I modified anything. I don't think I did, But That was over 30 years ago
I have a mechanical pump on the side of my 283. It is fed by an aerotex in-tank pump that is basically a direct replacement for the stock unit. Here is a video with the details: