Here you go, Craig. I had prepared something for JB just the other day. Let me know if you have any questions!
We use an RV mounted towbar with the brackets on Amphi. The initial theory was to minimize the look and water drag when not in tow, but to provide decent structure so that the weak front bumper bracket would not see too much load and so I wouldn’t pull the front end off of the car. She has about 73K miles of "towage", so far.
I have attached a couple of photos, plus a pic off of the Autocad file. If you have Autocad I can send the original.
As you see the actual towbar attachment is held on w/ quick release t-pins, so only the stubs remain permanently. As I did this originally when the car was positive ground (and the Amphicar braking circuit is open without the key on), there is a separate wiring harness for running light, brake lights, turn signals and a supplementary braking system I use. This Mil-Spec plug under the RH headlight is a lot less intrusive that the over-hood wiring tube I used to use.