"Hardened valve guides- - -"

I'm assuming you mean valve seats? I'm not entirely sure that would be necessary, but if you want to factor it into the price of the head rebuild, go ahead. Be sure the shop doiung the head work does a good job of shrink fitting the seats- - -a loosely-fitted one can come adrift and wreck an engine. I like to cut the counterbore for the seat about .0015"-.002" smaller than the seat ring, and freeze the seat in dry ice and alcohol to shrink it before it's driven into place. Heating the head in an oven or with a torch helps enlarge the seat counterbore, also.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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