I torqued the head back down with different rocker shafts on, and now the clearances are too tight and after backing off lock nuts it's very hard to turn square drive on end of adjuster.  What size is this across the square?  Is there a wee tool to make this easier?  It's too tight to turn by hand until I get it backed off.

i just use a pair of needle nose vice grips 

There is a tool to make things easier, like this:

 

 

Not sure how easy they are to come by these days. I am sure you can use a open ended spanner of the right size plus a ring spanner for the lock nut... Sorry cannot remember the size right now. 

5 mm just bought one off the snapon truck for that exact reason

where do we get such wonderful toys!!??

I just use the needle nose and a 12mm. tighten down on feeler guage a little because when you torque the bolt down it usually pulls back  on the cam follower bolt a little causing you to have to re- do it. i like the go-no go feeler guages because they have a ridge that lets you know when it is spot on.

intake should be 10 and exhaust 14.

5mm. Perfect. Thanks for your help guys!

Mind you 45 $ for one tiny wrench i will use twice a year