I sourced the 3mm x 20mm nylon bolts from Westfield and have fitted the running board rubber strips back onto the Morgan using the nylon bolts as positioning and anchoring while 3M double sided neoprene tape does the job of fixing the aluminium channel to the bodywork. I may make a small adjustment and fit 4mm bolts as the 3mm are fairly light and the square holes will just accept the 4mm size. The old bolts were 3.5mm and I did not find this size in nylon only 3 or 4mm, I went with 3mm but in hindsight should have gone up a size. I re-fitted the rubber strips using lithium grease as a lubricant and a trim tool as the muscle, it was quite easy..
Update on this, the 4mm bolt heads are 0.6mm higher and would cause the rubber strip to bump a little more when fitted and so I'll stick with the 3mm bolts.
