No Reverse Still

...Unscrew and Back-Out, the 'Back-Up Light' Switch!
Try getting Reverse with the 'Gated Plate' Removed...

I recently had the same problem with not being able to shift into reverse. The solution was to loosen the shifter shaft rod (which is located on the left side of the bellhousing), turn the rod so that the shift stalk is pointing slightly to the right but still centered front to rear, and re-tighten the shifter rod. Be careful with the left-handed thread shifter rod nut, which is distinguished by the "cut" lines on its edges. With this simple adjustment I was soon able to find my "lost" reverse gear.

My guess is that your shift rod moved out of adjustment at some point. I hope this helps.

Oh yeah, make sure your car is in neutral when making the adjustment I described above!