Thanks all for your comments so far.
To Western I think I have everything on P656, at least from memory, and the front two sections are certainly bolted in solidly which leads me to believe this as well. It's on P658, though, that I'm just missing the front bracket so you may be right and finding something to replace that is the best route.
I have to be honest I don't really have any fabrication skills but would anyone have any information on the bracket NTC3618 such as where it mounts or any images of it as I've struggled to find anything on it other than the image in the parts book and I don't think they are exactly renowned for their accuracy?