Do I have this table correct, for 57 y-block 292 with 1-5-4-8-6-3-7-2 firing order?

Yes that is correct firing Order. See Y-block Guy Site for easier way to adjust Valves. Easy way to adjust without Feeler Gauge on used rockers and Pushrods is 1/4 turn out from Zero Lash. U cannot get accurate Lash using Feeler Gauge on used Rocker Arms.

  

Because I deal with a multitude of engines with varying firing orders, I will simply rotate the crankshaft in 90° increments and follow the firing order in setting the valves.  Depending upon if the engine is at the overlap cycle on the #1 or the #6 cylinder at TDC, then I will start setting the valves on the cylinder that's not on the overlap cycle.  With this in mind, I do not have to start on the #1 cylinder and only two revolutions of the engine are required to have all the valves properly set.

Here’s a link to a past thread discussing different methods for setting the valve lash.
Setting the Valves

Performing search on this site will bring up a number of past threads on the subject.

Lorena, Texas (South of Waco)