I removed the part of the hinge attached to the bonnet and drilled out the pin with an 6mm drill.
Then I masked off the area around the part of the hinge that was still attached to the car and drilled that out with an 6mm drill....
When I offered up the 8mm Clevis pin I found the hole in the bonnet part of the hinge was bigger than the Clevis pin - WTF!!!???
The Clevis pin fitted perfectly into the part of the hinge still on the car .....
I can only presume that when I was drilling out I must have drilled at an angle, even though I used a 6 mm drill, and that must have made the hole too big. I had drilled as close to one side of the pin as I could, reasoning that when I got through I would be able to prise/lever the pin out .
Anyway I cut the Clevis pin down to a size that it would fit between the bonnet and the windscreen rubber surround and secured it with a split pin ( and washers ).
When I closed the bonnet there was no movement in that corner of the bonnet - now I am even more confused - the bonnet must "bend" slightly when closed resulting in no movement from the pin. I think I will ultimately have to replace the hinge, as knowing its like that is annoying me - that or I drill out the body hinge to match the diameter of the bonnet hinge pin hole.
What the hey, I did buy it as a project car - looking forward to getting my fingers dirty and that is defiantly what I am getting.