[Excaliber]

OK this all sounds very weird because no one has mentioned the fact the block should be measured for "square" before decking.

Measure deck height at each corner of the block and compare that number to the stock specification. If the block is NOT square it's a no brainer, gotta deck it.

If it is square and it passes a flat test using a straight edge and a feeler gauge there is no "normal" reason to deck it at all.

If you want to get fancy and go for zero deck height (not a bad thing) or some other "race ready" reason, then deck it.

What bothers me about this is:

Why didn't your machinist measure the block for square before recommending he mill the block? I don't like doing things "just because" thats the way the machine shop always "does it".

Deck height is measured two ways:
From the center of the crankline to the top of the block. This is a VERY difficult measurement and requires special "tools". I wonder if the machinist can do it? The other way is measure rod length and piston pin to top length, stroke and then do the "math". BOTH sets of measurements should agree with each other. YOU could measure your rods and pistons yourself and compare that number to what the machine shop said it was.