My Chevrolet Express van Class B- camper

I took a picture of my already mounted seat swivel. It came with two mounting bolts welded in place. I mounted the side with the welded in bolts to the bottom seat rails still bolted to the floor. The top side of the seat swivel was where I drilled the new holes for mounting the seat. The new holes were almost over the top of the bottom holes and I had no problem with the top bolts hitting the bottom bolts when I swiveled the seat. The top part of the seat swivel had a large part sticking out on the side to the center of the van, so I cut that off so my seat trim would fit over the top of it. You can see in the upper left corner of the seat swivel in the picture below that the corner is shiny where I cut it and ground off the corner as I did not repaint it yet. I hope this info helps in your project. You can also see the 6-wire connector I added so I could thread the seat wires through the center hole. I soldered all wire connections to make sure they did not come loose as the van got older. Because of the close clearance I had to lift the seat up to start the nuts on the seat bolts and only tightened them when all the nuts were on and started.