I used the standard Marlin supplied brackets but there were two versions, one made from solid rod and the other from tube. I had the solid ones and they were fine while I had the car (and still are as far as I know) but the tube ones failed for most people as I recall.
Patrick is the one to ask. He made replacements for his Marlin supplied brackets. I think you will find plenty of pictures on his website.
www.msportster.co.uk.
Cheers, Robin