Help with decking or not?

Agree with RRR
we used the popular BHJ tooling which locates the cam and crank and makes it easier to get everything square, ( and do the lifter bores dead nuts on if necessary
AS RRR intimates shops without the proper tooling have been known to use stepped reamers to do the lifter bores for bronze bushings and they end up all over the place
and are a ***** to straighten out- have to go to oversize bushings
I was thinking of the Mr gasket .028 also less expensive
Cometic needs a finer deck and head finish- Mr gasket could use also but Mr Gasket can use the more common finish
Do the Mock up and measure as I suggested and then calculate compression if the pistons have a dome or dish you can do a pour of cc with the cylinder vertical
and really nail the compression but then again the piston vendors cc numbers and the deck height should get you close since most likely u do not have unknown cc custom pistons
measure all four corners - you may or may not have to deck your block
I've had blocks that I wanted to 0 deck based on the pistons and rods (440 six pack pistons, KB in one case) but ended up with them .015 out just to get the block squared
Then I had to use a .050 gasket to end up with .035 quench on one .030 on the other
hope you get lucky- most do
get back to us with the measurements
glad you are doing a mock up- only way to get it right
last few years doing mopars I'd deck the blocks minimum square when doing the bore procedure
then mock it up and cut it again if necessary