I see that John Hubbard's 1957 MGA has seats with headrests. What car was used to source these seats? Were any interior modifications needed for them to fit?
Jeb Blanchard
Those are late NB Miata seats. Miata guys call them "Surfboard seats". They are too tall IMO. The NA to early NB seats will look better as they are not as tall.
Surfboard seat compared to NA Miata seat:
https://forum.miata.net/vb/showthread.php?t=683272
Mine are 1999 NB seats that are shorter than the Surfboard seats:
http://www.britishv8.org/MG/CarlFloyd.htm
Rick Ingram recovers & sells NA Miata seats for conversions. They fit in an MGB. Should also fit the MGA.