From B.O.C newsletter, Vol 1, Number 4, June 1975
FLOOR: Hints on mending rotted-through floors: Reinforcing box beam along door sill on the inside.
1. Remove seat, aluminum threshold (as explained in earlier post) and narrow rug under threshold.
2. Determine the extent of rust: only along front floor pan, only along back floor pan, along the whole side.
3. Try to remove as much rust as possible to solid metal.
4. Use 16 gauge (1/16”) ‘sheet metal or thicker (galvanized, if possible – but be careful if welding). A one inch lip is needed for riveting to the floor, Thus, the sheet metal will have to be about 6″ wide. Measure carefully from the firewall (NOT the rug and backing) to the cross brace, If not running the full 6′.
If running the full length, measure carefully, as it is not exactly 6’. If the reinforcement is to run the full length, decide whether to notch for the crossbrace (above) or to cut it free from the sidebeam, fastening it later to the new reinforcement. If the seat bracket is loose or breaking, it will have to be fastened to the sheet metal later. Be sure to take an accurate measure from the seat track to determine exactly how far from the slot in the cross brace to the slot in the seat bracket, (just shy of 16″ center to center),
5. If you plan to salvage the original Vigot jacking system, weld or braze braces to this side as you did to the other side of the jack mounts before fastening the reinforcement. The mounts through 1958 are longer, thus can be strengthened more easily.