Rick,
Sorry for not getting back to you earlier. Pity that it's JCB, but it does confirm my presumption. I mentioned that the open ends of the "A" were spot-on, but later I realised the Conger ones are straight and the JCB ones are slightly angled....so the ends are also different.
The original towing frames used for the Conger, were also the ones used to tow the "gutted carriers"...stripped carriers to carry material. There is a series of pictures of two of them during the liberation of Culemborg, towed behind Churchills. Rick....you can modify the JCB frame and throw a canvas cover over a stripped carrier, tow it behind your AVRE....and.....
Alex