I'm going to steer you in a different direction.
There is, to my mind, nothing especially magical about BBD chips when it comes to achieving longer delays. As long as the word-size is at least 10 bits wide, the sample rate high enough, and the filtering appropriate, digital chips will sound almost identical to analog BBDs. Whatever it is you like about the DOD 680's sound is likely to come out of the specific filtering used and not the BBD chip itself (although there ARE inter-chip differences in signal handling, noise levels, supply voltage range, etc).
Scott Swartz's PT-80 project (found over at
www.generalguitargadgets.com) has been very favourable received here by many builders. Although it uses a Princeton Technologies PT2399 digital delay chip, once you factor in the companding and lowpass filtering, most users are hard-pressed to find anything wanting in it as a medium-length delay circuit (fairly uncommon to see single-MN3005 or SAD4096-based delay pedals with more than 350msec delay time or less than 250msec). Unlike the MN3005 or the SAD4096, the PT2399 is in production and relatively inexpensive (try to find one of those other chips for $5!). Getting the sound you like may simply be a matter of adjusting some of the component values in the filters or compander.
Of course, sandwiching the PT2399 into your just-about-ready 680 board is another matter, and quite possibly a non-starter. If you don't have a mostly-populated board at the moment, do consider the PT-80 or its cousin the AD-3208 which uses a pair (or trio) of BL3208 chips, what is commonly understood to be the only medium-delay (2048 stages) BBD chip currently in production and available for reasonable price from Small Bear Electronics.
Finally, although *functional* pin equivalences for the MN3005 and SAD4096 are identifiable, the parameters of each are different. For instance, the SAD4096 is powered by a positive voltage, where the MN3005 uses a negative supply voltage.
