new valve seats in a 1970 bonnie head

I have a head with deeply cut seats. Spare bonnie heads are hard to find. Can new seats be installed? Aluminum has been cut away from the valve area.

The seats are trapezoidal and cast into the head, a very skilled machinist with a proper serdi can machine out the old seats parallel without removing alloy (leaving the circumfrence of the old seat in place), and press in new seats. I had this done on my T140 head, seats are better than new

http://enginedynamics.com/ This machine shop is the only place I would use for Triumph valve seat replacement.