Aftermarket seat mounting

[smittys69]

I purchased a used set of flat bottom aftermarket seats for my 69 camaro and am having difficulty using my old sliders with the new seats. I had to change the mount as they did not bolt right up and since they are flat bottom, it raises me up now where my head is touching the headliner. My other option is to make "fixed to drop them down to the proper height as I'll probably be the only one driving it anyway. Anyone else have ideas or methods used to get around this and still have adjustable seats? Thanks