yep, if you want to keep your cr as it is (which will typically be higher than std as most heads have now been skimmed) then just get the standard one.

There are more than 2 thicknesses available for most engines, altohugh ive only used standard on a YB so cant confirm the options for that, but on the vauxhall engines they do 3 or 4, including one thats thinner than standard.