My son has  a Mazda Miata which he plans on racing, therefore he is replacing his seats.  These are the most comfortable sports car seat I've sat in.  They have a recess in the headrest for two stereo speakers.  When driving with the top down you can actually hear stereo!  

Serious Auto Accessories sells leather seat covers for Miatas, and they have over 50 colors available. They can glue and stitch a Triumph or any patch you provide for a nominal fee.  This is the photo I sent them to see if it could be done.  Alternatively, they could transfer your design and custom embroider a logo onto the leather.  This is a bit pricey though; $200.00 for the set up and another $30.00 to have embroidered.    Larry Cohen  of  "Serious Auto Accessories" said there would be no problem putting a user supplied jacket patch.  The seats alone cost  $550.00 a pair, which compares favorably with leather seats ordered from Newton Commercial in England  or Spitbits here in the US.  I'll be using Midnight Blue for the rest of the interior vinyl and will send a color swatch to Serious Auto  to see if they can match it.

This photo illustrates the perforations in the                            headrest  for the two stereos--------------------------------------->

Dave West has a set in "The Beast" and has posted the brackets he fabricated.

Mark Campbell spitfire@shelby.net  felt the seat mounts may be able to be flattened out (they are angled). After flattening the mounts, he thought he could use a 1" wide piece of stock to span the floor and mount through that.

check out Dave's page at  http://www.westpro.com/Beast.html

and the Miata seat stuff is at http://www.westpro.com/Spitfire/Beast_Folder/Beast_Tech/Seat_Talk.html