After purchasing my 'possible' Arrow based 50's mud plugger, I have been looking into all things Arrow related. It seems there where quite a few variations and I think the previous comment of no two being the same, could well be correct.The riveted bonnet, does seem to tie in with other known Arrow's and there does also seem to be different variations of the wing stays. With cars of this age, there is plenty of scope for alterations by their many owners, so who knows really what was original - with so few survivors and so little documentation. A few more pics below, the navy one does seem very close to the one in question.
Different wing supports:
last pic taken at a show last year
Different wing supports:
last pic taken at a show last year