For historical accuracy you won't get anything more definitive than John McGlinn's 3-Cd set of the entire show plus various cut and added songs, nearly 4 hours of SHOW BOAT material.
http://www.amazon.com/Kern-Hammerstein-Frederica-Sinfonietta-Ambrosian/dp/B000I2ISLS/ref=sr_1_13?ie=UTF8&qid=1287782741&sr=8-13 There is also a single disc of highlights but it sounds like what it is: bits clipped out of a longer recording.
If you want a single disc of the key numbers it gets a bit trickier. Livent's disc of the 1993 Toronto production is quite good but it preserves a revised version, and while the performances are great, it is a really "dry" recording - no reverb at all. It's also out of print; mixed in with Livent's assets it could be a long time before we ever see it released again. But used copies are fairly plentiful, and inexpensive. (There are several used copies for ONE cent each!)
http://www.amazon.com/Show-Boat-Premiere-Cast-Recording/dp/B000001ZBA/ref=sr_1_44?ie=UTF8&qid=1287783631&sr=8-44 Although not authentic, the Columbia studio cast with John Raitt and Babara Cook is quite enjoyable, but it has been sanitized into a very "white bread" SHOW BOAT.
http://www.amazon.com/Show-Boat-1962-Studio-Recording/dp/B00004THLR/ref=sr_1_7?ie=UTF8&qid=1287784267&sr=8-7 Beyond these discs is mostly a pick and choose to get your favorite version of each song as no single disc has everything.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com
Updated On: 10/22/10 at 05:54 PM