how much too deck the block

[jodowii2]

plan. 258 stock bore and stroke. have a 4.0 head ive had .020 cut off
block is out for cleaning and was going to have it decked.
head gasket measures .040
have a crower baja beast cam on the way. as well as the lifters and valve springs they recommend.
this cam is supposed to work with stock pushrods, that being said. how much can i deck the block before pushrod length becomes an issue. how much will this change compression?

what would you all do?