I really should of taken more pictures when I did it, lol.
What I did was purchase and inexpensive, small car seat slider. You know the mechanism that slides your car seat forward and backwards. My buddy suggested a riding lawnmower seat adjuster, but I happen to come across this one for fairly cheap (about $30 USD I think).
I got is all measured out and figured out and then went to work.
I used 3/4 plywood that I sealed, 14x15 pieces I think, and carpeted.
Took two 2x2's and ran them the length of each base plate (left to right).
I notched out both 2x2's so I could put a 1x2 across (front to back) for extra bracing.
Put a standard 7" swivel seat base on and marked the holes.
Then I clamped everything together to drill holes for the bolts.
4 holes for the seat base. Through the seat base, 3/4" plywood and 1x2's.
4 holes in each corner through 3/4" plywood and 2x2's. They match up with hole on top of seat slider.
Everything is carpeted and ready at this point.
I put a bolt through the 3/4" plywood, 2x2's and bolt to top of seat base slider. All four corners.
Then I mount the seat to the swivel base, then mount to base. It was a little tricky and took a few minutes because of tight space. But patience is all it took
At this point, the whole seat base is attached to the sliders.
Now I just slide the base where I want it. Mark the holes and drill through my seat top and put toggle bolts down through the hole and tightened everything up. Took a little to be precise, but it worked like a dream.