DP 35 was 1971 which would be the modded EB3. I'm actually in the process of duplicating that instrument using a basket-case 1969 EB0, Dark Star pickups, and other tweaks. For now I'm using a DeArmond Starfire with Dark Stars, Bartolini EZQ filters, and a DTar eclipse buffer.
What I believe are important to getting the 1971 sound, in this order, are:
1. Flatwound strings. Roundwounds with the tone rolled way down are a mediocre substitute.
2. wide pickups, preferably darkstars. Wider pickups pick up more frequencies, for a fatter, rounder sound. Darkstars or Mudbuckers are ideal, J-bass pickups are the oppposite example.
3. Short-scale neck. (The Epiphone Jack Casady seems to be a great way to get close to the right bass on a budget and possibly also the closest way without getting custom work done)
4. Warm, flat-frequency amp, preferably with a little grit. Personally, rather than going with a Showman or similar heavy, unreliable and underpowered Fender head I'd go with any modern bass amp with a good, neutral tone and put a Sarno Earth Drive pedal in front of it for warmth and grit. http://www.sarnomusicsolutions.com/products/ed.html
The fender head may work if your band is way less loud than most of mine.
For speakers you'll want 15"s in as neutral of cabs as you can find. The ideal would be JBL D140s in cabs that duplicate the designs of the era. The closest commercially available would be http://www.hardtruckers.com/HT215B.html
I've heard great things but have not tried it myself.
I have played Phil on my P-bass. It works ok in a pinch but I find myself altering my physical playing techniques to try to approximate the sound, whereas on my Starfire, even though I'm less comfortable on it overall, the 70's Phil sounds come out of it more naturally.