Not to get into a food fight with the very knowlegeable Jack, but the same support is used for the M40 and M41 -- and it's different from that AT support, as you know. I doubt you'll be able to buy this part new, although it should be a common item... look for someone who's parting out a manual 122.

The problem you'll face is that the floor sheet metal is different on AT and manual cars, and there's no built-in place to mount the manual support. The AT tunnel is wider, and there are no blind nuts in the box sections for the support to bolt to. You'll have to fabricate something.