I appreciate it may not be a direct help but I have a Howa smithed by Pete Lincoln aka Roedale in Germany. He is the Howa accuracy specialist there,and builds on his own actions too...
He has written on several boards (inc The Hide) about the strengths & potential and how to's of the Howas .. Under his own name ... could be worth a search?
Truing/blueprinting of any action is basically the same, the methods may be different but
the goal is to square and true all surfaces that you can based on the center line of the
bolt including the bolt it's self and the fit between the bolt and the receiver.
The Howa,s make fine custom rifles and stocks and aftermarket triggers are available
I recently picked up another Howa 1500 long action that I am considering making a 6.5-280AI. It's kinda interesting because this one has a really decent trigger unlike my .223 which took a freight trane to pull the trigger no matter how much I adjusted it.
Thanks for any and all information guys much appreciated.