Stator / Rotor air gap adjustment ?

... a bit of clearance of the studs in the mounting holes and the stator can generally be persuaded into place. Leave the nuts just catching and give a gentle tap with a rubber hammer in the desired direction.

I think the original instructions were to use feeler gauge strips around the perimeter of the rotor (when it has been fixed in position) and then bolt the stator on.  There is no adjuster, as such, but the feelers should maintain the gap when you tighten the bolts.  Many years ago I used to get the gauge strips from Vauxhall dealers, but you could use 3 feeler gauges - if you have them.
Dunno what thickness you are supposed to have as I haven't found the required air gap data yet.

I hope you meant 0.008".  And that's a minimum gap, checked at all core ends, with crankshaft rotated right round 360 degrees.

There have been reports on https://www.accessnorton.com of Wassell's new "Lucas" stators burning out, which may be caused by lack of clearance leading to rubbing.

This is the season for this hardy chestnut which I have responded to in the past and one that I have carried out myself.
I followed Norman Whites tip by reducing the retaining bolts down to their core diameter i.e. the bottom of the thread depth, the plain area behind the threads.
This allows plenty of leeway for adjustments to attain .008" using feeler gauges around the periphery of the rotor.

Has been my gauge of choice. No magnetic movement and easily cut with scissors.  Of course keeping things imperial....,   I always use "Inches" .

Hve met this problem many times. I position 6 pieces of plastic milk bottle strips around the rotor before tightening the (slack) stator stud nuts. If still too tight, you can enlarge the stator holes slightly by careful filing. This has always worked for me and no burned out stators!

If you use this method for reducing the studs to get the clearance, then the stator might just move back! in which case you are worse off than when you started.
The following has been done BUT is to be done with a lot of care. You can file the inside of the stator BUT that would invalidate any guarantee. You could also invalidate any guarantee by turning a A FEW THOU off of the rotor.
PS Just be thankful you do NOT own an AJS/M!