Huddie
I purchased a tool on evil bay that was made for VW air cooled engines that claimed to be suitable for A10's and it worked great.
Heated up the cast head in the BBQ and gently drifted them out from the combustion side...they came out without any dramas or butchery
At a later date I had the auto machine shop install the new guides as they were re furbing the head for me.
They asked me for the bore/tolerance of the guides as they wanted to make sure the clearance was correct with the valve stems.
For this I referred to the data in the Haynes Manual:
A10 Valve Stem dia when new Inlet 0.3105 - 0.3115 in Exhaust 0.309 - 0.310 in
A10 valve guide bore 0.313 - 0.314 in
They did end up machining the bore of the guides.
hope this helps
scotty