I've thrown away several 'good' 302 blocks because they are a lot around. On the other hand, a 289 block is relatively rare as the 6 bolt version was only used from 1965 to 1968. If that 289 block has a casting part number of C5AE-6015-E and a date code with the year of either 1965 or 1966, it may be more valuable than you realize.
Jim