I would suggest you go to
www.myMopar.com find the appropriate schematics for under tools/references for your car, the gauges are supplied by 12 volts {pink wires, from the fuse box, if I remember correctly}, then go thru a voltage limiter, that reduces it down to 5 volts for the printed circuit board, that the gauges get their feed from, Evans Wiring Harnesses or M&H Wiring Harnesses {Year One Exclusive} are easier plug & play original type harnesses,
but the Painless Muscle-car harness can be done easily too, follow their instructions & the wires are all marked really well... you could try Mad Enterprises @
www.madelectrical.com for the connectors, plugs etc., schematics/diagrams & some great tech information too... if you run into problems call the tech guys at Painless Performance 1-817-244-6212, they are great people too... also a
1969 Plymouth Factory Service Manual, will help also, it has a bunch of great schematic/diagrams too... you can get color schematics/wire diagrams from Year One still too "I think"... I got some for my 68 RR's a few years ago, easier to read than black/white drawings/diagrams... I don't have a scanner or digital camera that will work with my new computer, or I would just post them all for ya...
Good Luck &
make sure to take your time, take/make some detailed notes, especially when taking stuff apart {keep all the connectors & ends}, make sure to keep wires away from heat & moving parts, you may need to reuse a bunch of the original connectors, if you can't get replacements... I would highly suggest to use, zip ties, soldier & shrink wrap everything, then tape /wrap wires, not just the cheapo crimp style connections, make tabs & easy to identify labels, so you can find stuff easily, especially when under the dash, it's a PITA unless it's removed the gauge panel at least, you will need to drop {just lower} the steering column to get the gauge panel access out, makes under dash stuff much easier...