Edelbrock heads on a 340 with KB243 pistons
Here's a quick breakdown of some others I found.
Edelbrock 7326 .050
Mr Gasket 1121G .028
Mr Gasket 3211G .040
Mr Gasket 5805G .038
Cometic offers everything from .028 to .051 in .002 increments and then jumps to .060
FelPro 1008 .039
FelPro marine 17050 .049
Oddly enough the only one that didn't have a compressed height advertised was the FelPro 8553 which is the most common one.