GRIEF ! is what you get when you receive your new voltage regulator and you don’t read the instructions first, resulting in a serious mistake and followed by depression of such a nature as to tempt you to stick an  ice-pick in your naval or some such act of equal silliness !!.
  That having been said, I must assume you know for sure that your old voltage regulator is defective (with your key on, you have 12 volts going into the old regulator - brown wire- and no voltage coming out - red wire w/ black stripe connected to fuel gage – and that your ground is good – black wire-). If you have 12 volts going in ( brown wire ) and you DO NOT have 7 volts coming out ( red wire ) your regulator is defective. Ready to go forward? Good!

1) First unscrew the old fuel gage voltage regulator do not not not lose these little screws, if you do depression is sure to follow, these little buggers are the only ones that fit.
2) With the old regulator in your hand cut the brown & black wires as close to the old regulator as possible. Then disconnect the red wire from fuel gage.
3) Now take those little buggers and mount the new regulator with the wires facing away from the fuel gage terminals. Yes, I know it’s a close fit! See what I mean about these little screws?
4) With the face of the tach down rotate the fuel gage terminals to the bottom right corner as shown in photo. Route the fuel gage wire – red w/ black stripe- under the brown & black wires along bottom of regulator and unto fuel gage terminal. It only fits well one way.
5) STOP! Before stripping wires on new voltage regulator, grab WIRE then strip. DO NOT GRAB
REGULATOR BODY! Now before connecting brown-to-brown & black-to-black consider this. It is better to solder wires together but barrel connectors are supplied for your convenience. In either case install heat  shrink tubing before making connections..
6) There! Now don’t you feel better no depression or ice-pick in your little tummy?
7) Also have photo below for those of us who aren’t so great with written instructions.
8) Now you’ll have 7 volts at the red w/black stripe wire side of your fuel gage. If you don’t we know this,your voltage regulator is good and you have a problem somewhere else. Try this; bad fuel gage or sending unit in tank or bad wiring.