looks like a 55 would be a 331
http://www.allpar.com/mopar/hemi/oldhemi.htmlChrysler hemis are the easiest to get parts for. they are not cheap motors to rebuild.
as far as value, for an unknown motor, maybe around $600. early hemis are not cheap and everyone seems to want them.
last year I bought a really rusty 56 330CI desoto hemi for $150 I worked on it for about 2 weeks and could not get the pistons out of their bores(I tried many methods), it now sits in the corner of my garage waiting for me to have more time to work on it.
a cool(hot) pic of it-
