It is really 2048; the databooks claim the upd553 is some non-power-of-2 ROM size, but it really is power of 2. Kevtris has a rig set up for dumping upd552 and 553 (and upd650), IIRC it involves selective insert of NOPs and 'jump following' to dump the entire ROM, it isn't straightforward.
The Hitachi MCUs on the other hand have a built in test ROM which can be used to bank in any page arbitrarily and are somewhat more straightforward to dump, if I remember right.
"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"