Is there a full front/rear body kit for the Manta at all? I am trying to decide to go with that or stick with the 1974 bumpers. There was one picture I saw with a new front end that looked great, but don't ask me to find it again.
I'm sure Irmscher or Steinmetz did a kit for them back in the 70's. I can remember when my dad owned an 'A' series GT/E Limited Edition known as 'Black Magic' and was offered this kit by a local dealership in Germany.......dad turned it down.
You could try a company like Lenk in Germany or search on the web.