when a piston is rated for say 9:1 cr for a b18c, is that with the block not being decked at all and with stock size rods and crank?? Ive went to websites that will say the piston to deck height but is that height only different then stock because the piston is different??

 

yes if a piston is rated for 9:1 compression that is assuming you are using the stock rods/crank and that the block has not been decked

look up a compression calculator and you can figure up your compression with different rods

here is an example of a calculator:
http://www.knology.net/~jediklc/D.htm

 

try this one for a b series

http://zealautowerks.com/