For hydraulic lash adjusters in general across the world of engines and baring a specific measurement, 1/2 compression is about right, this gives you room to take up for wear of the cam ( adj extension ) and compression to account for valve face wear ( adj compression ) .

The preload was probably increased late 82 to take care of a cold start valve tap.

You've got the theory down right.

The lash adj will need time to bleed down so make sure you are not forcing the valve to be open. I've put various motors together that would run rough until the lifters bled down so the valve were not held open Past that, this isn't something that you have to fight 0.001 "

I'd measure full compression of the adj, pop the parts together with the cam at the low spot before the adj expands, then measure how far it extended.