b.o.p ?

any pros or cons on a b.o.p 455 ? i'm not sure what it is yet,but it's cheap, and i was considering buying it. i'm thinking it's a pontiac 455. where could i find some more info on these engines. i'd like to find out some of the casting numbers so i know exactly what it is. if it's a desirable casting i'll buy ,but if it's just run of the mill i'll probably leave it in his barn. any ideas on what to look for to figure out what this is ? possible worth in rebuildable condition ? thanks tim