I took the time last weekend to fit, and approximate where the seats will go. Toyota was nice enough to leave the space where the they attach unstamped when they assembled the vehicle in '86.
Both seats can rotate 180ºand recline without issue. Once the position was satisfactory, I marked the feet position and used a metal punch to centre where the drill hole will be going.
I will have to drop the gas tank, to make sure I have clearance for the drill holes. I'm confident there is; but I need to remove the fuel cell for two reasons.
A) I need to fix the fuel gauge sensor inside the tank.
B) I refuse to weld with gasoline in the van. Especially right over top of the tank.
In my spare time, I'll be making templates that I can transfer to 1/4 steel plate, which will be used as an anchor point. I will then weld the plate to the sheet from the top, being careful not to burn through the floor pan.
I have some concerns about welding plate to sheet metal, especially thin autobody metal. I may look into an industrial adhesive for the plate instead of welding. We'll cross that bridge when we get to it.