Dunno if anyone's still reading on this thread after all that rediculious squabbling over various subject matter, about 80% of you are right in what you're talking about, but not many are really answering what the guy wants.
Anyway, to the original poster, i'm an avid jack bruce fan, and whereas you're only trying to cop his tone for a few tunes, it's what i bass (bass, base, lame puns) my playing style around. I started out on an Epi EB-0 like you, fell in love with it, played it through a peavey solid state head with a 2 10cab of guitar speakers. Now i've changed my cab to 2 10/1 18 and a 2 15 cab, with an epiphone EB-3 and a late 60's gibson EB-3
I get the feeling you're on a budget if you're only playing an epi EB-0 (not a bad model, but it IS the bottom line). For about 400bucks the EB-3 can be yours with a bridge pick-up to get closer to jack's punchy tone.
To get that fuzzy/ farty tone, i just plugged into my digitech jimi hendrix experience pedal. I know, it's voiced to create sounds off hendrix records, but it can give you a good marshall vibe. Nothing matches a good tube head, but we're not all made of money, otherwise we'd ALL have one

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ANYWAY, the hendrix pedal is good for marshall drive sounds, but you lose bottom end, and the pedal is a bit expensive to use it for one thing (cost me 300 bucks, but i also play guitar)
Your best bet for a cheap simple way to get that fuzz tone is an electro-hamonix big muff for about 100 bucks. Easy to find, reliable, and good low end, but sometimes i feel it's almost TOO fuzzy for jack tone. If you play in a three-piece, this is a GREAT pedal to have, it's not too punchy or upfront but it fills up the sound like nothing else.
I'm personally going to look into getting an electro-harmonix english muff'n. Same tubes found in Marshall amps, so I'm guessing it might get me closer to tube drive without totally changing my rig.
If you're feeling like something is missing...
Lots of guys say tone is in the fingers, and anyone will tell you jack is a very agressive player. He was an upright player, and anyone who's had the misfortune to play a poorly-made one will tell you it take some serious strength to make those gut strings talk without an amp. Start plucking every note loud an proud, just like jack. I do it too, but remember, jack played through tube amps back then, and ANY tube lover will tell you the effect your fingers will have on the dynamics. Pluck harder and it distorts more.
Cream was famous for their jamming/improv skills, so you need to throw a little creativity into your playing here and there if you're covering Cream tunes. Jack has an amazing sense of time, and as a cellist so he understands melody and counter melody, so keep that in mind. When he played in the grahme
bond organization and Cream, he deliberately tried to play his bass like a guitar, challenging clapton and driving the band during their extnded jams.
People drawing comparisons between 60's cream and the reunion shows are missing the point that clapton hasn't played in a three piece band SINCE cream, (blind faith had 4 people, derek/dominos/solo career had 5+ musicians in his band).
Over the years Jack has returned to the fundimental role of BASS player, so he still adds in counter melodies, simply because that is just his style of playing, but he is definately more restrained.
And their gear rigs have been completely remodeled, jack through gibson/warwick and harkte, clapton through fender and fender, so their overall tone will be totally different.
This will definately give you a Jack VIBE, maybe not his exact tone, but personally I've been happy with it, so use this information as you will. If you're that serious about it you can try to copy his technique as i have, but overall, you'll have a jack vibe and sound, but you yourself will still shine through, which is what we all want, right?