When I was thinking about replacing footwells in my now departed '74 240D, Randy Steele at European Parts Specialists
www.epsparts.com could get them - not too expensive either from what I remember.
Good luck Mike, I always enjoy hearing of de-rusting and re-painting of good cars like these. Something almost spiritually rejuvinating about extending their life in such a dramatic way
Looking forward to hearing about the progress.
Regards,
- Ryan