Here are some pics of the demo and build up of the floor - Sorry, but I do not have a close-up of the L-track and seat mounted to it, but can take one next time I go up to the bus:
Seat removed and heater panel cover off:
Before removing the seat, I went under the bus and spray painted the four mounting bolts so I knew where they were when I installed the new flooring...
With heater core/blower removed:
(Note original plywood flooring is still in place.)
After removing original floor and priming/painting the base metal:
Before covering the front floor with 1/2" plywood, I put a layer of Kilmat down for a
slight noise and thermal barrier. I also bolted 2 pieces of the L-track (about 12" or so each) to the floor using the original seat bolt holes, and cut out slots in the new plywood to accommodate these...Did this to avoid getting too much rise on the seat when reinstalled. This is the L-track I used:
this came from the overhead and was used to secure the wheelchair shoulder belts...I also had a boat load of flanged L-track like this:
...which is what the passenger seats were bolted to, but did not want to chance the clearance below the flange matching the plywood thickness.
Hope this gives you some ideas...not sure what your bus is or how the seats were mounted, but I have a bunch of the flanged L-track if you need any...just not a lot of the track fasteners (last pic above), but they are available on eBay or I think Amazon...