I have been wanting to upgrade the seats in my MGB GT and the choice really came down to 1969 or later MGB seats or first generation Mazda Miata seats. The main reason for an upgrade? I want to have head restraints and install a 3 point harness, the idea of crunching my head against a metal and wood steering wheel isn’t appealing. I’ll definitely be keeping the original seats so that the car can be returned to original if ever desired.
The Miata seats are certainly light years ahead in terms of support and are very comfortable. Eventually I’ll cover them in a vinyl or leather that matches the interior better but for now the old cloth will do. It looks relatively easy to make the adapter plates that are required although I know that a few people are producing them if you’re prepared to spend about $150 or so. I’m thinking about $15 and some paint will do the job.
I’m looking forward to this project, in the meantime I can sit on Mazda Miata seats in my office, maybe I should get an electronic steering wheel and do some iRacing!

