SSH isn't included per version page. The router database confirms this only has 2MB & the peacock thread advises that it can only do micro. It advises (& other links below) you have to compress CFS to move to another version:
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=289931
http://dd-wrt.com/wiki/index.php/Linksys_WRT54G_v8.0_%26_v8.2