Not a lot accomplished today because I was on baby duty most of the day but here's what happened:
Started with cutting out the trim holder / wire shield to pick up some room well-to-well
Next cut and big hammered the factory brackets away. The sheet metal is surprisingly thin there, the first one I did I didn't quite make it through the seam weld and it tore some of the sheet metal. I'll square that up later. The other side came out with issue.
Next one of the brackets for the seat was too tight to the tunnel causing the rear seat to sit out of level. Drilled the spot welds
So I can move the bracket over a few inches.
Ending with the rear seat fitting almost perfectly.
For attaching the rear bottom, the mounts are pretty straight forward. I'm going to weld some captive nuts to some 3/32" steel plates, then weld those to the chassis. This should make the mounts for the seats (I'll do the seatbelts the same way) plenty strong. Probably way over kill but rather be safe than sorry. I also have the factory s40 "LATCH" (car seat) bracketry. I'll employ the same system for that.
The back rest portion of the back seat will be a little trickier as it's really tight to the wells. In all reality, I'll probably end up having to open the guts of the seat, taking a page from
John r h's thread and do a little surgery. Not much honestly, they are a pretty damn close fit as is.