Help on Animal - derailleurs, Chain ring & Cassette

[forthefunofit]

My 1998 (yes I'm the first and only owner) needs some TLC.  Been riding and not paying attention to repairs.

Local Bike store wants to slap on Shimano Alivio - I want to keep as pure as possible. I'm new to bike repair, like working on bikes almost as much as riding.  My research shows:

Front derailleur - top-swing, bottom-pull/clamp-on 31.8mm.  Is it FD-M739 or FD-M739 E (E plate style) (top swing)?
    Can it work with "FD-M950, and FD-M950-E (bracket type) with differential plate and top swing link"?

Front Chain ring and Bottom Bracket.  There are a few options:
         FC-M739 4 arm or 5 arm cranks,  BB-UN72 or BB-UN72E for E plate derailleur (sealed cartridge type), available in 22/32/42 or 22/32/44  rings, 165/170/175/180 lengths, cups available in English (68/70/73 x 107/110.5/113) threading?

Rear Derailleur.  Is it RD-M739 GS (mid cage) and RD-M739 SGS (long cage)? I think SGS
       Can it work with Shimano XTR RD-M951 Rapid Rise?

Rear Cassette.  I thin it's CS-M737-I cassette - right?

Thanks for your help!!  Brian

[shovelon]

113 mm is the bb length. I know that much. So almost any crankset you buy will determine the chain and rear derailuer. The front deraillieur I would get in dual pull just in case you want to swap it to another bike.

My Beast came with SRAM. What about the Animal?

[forthefunofit]

Thanks for the pointer on bb.  Animal came with Shimano Deore XT groupset.

General useful links to show original components of all bikes:
   http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?year=1998&brand=K2&model=ProFlex+Animal
   http://www.bicyclebluebook.com/bicycledatabase.aspx?make=928

Useful link Shimano groupsets:
     https://en.wikipedia.org/wiki/Shimano_Deore_XT
     http://mombat.org/Shimano.htm#1998