Vectra valves in 12G940 heads

 Looked at a Vauxhall/Opel/GM Vectra head that had gone to pieces.  The
exhaust valves are the same dimensions as the Midget with the exception of
the length of the stem (longer by about 50 thou) and the diameter (narrower
by lots).  Since it appears to be a stainless steel valve with flat back and
narrow stem, is it going to be of any use to the 'fast boys'?  Individual
valves come at about #19 each, slightly higher than steel normal valves.
How much for the stainless ones?