Petrol tank fixing

I'm fitting a new petrol tank to my 1977 88". I see in the parts manual the fixing bolts have big rubber washers which seem to insulate the tank from the outrigger. There were just normal rusty bolts on the old one. Are these important or can I just bolt the tank on using ordinary bolts.

i used one of them rubber squeegees fer grouting. smash the wood orf and cut the rubber into usable size bits

they say an elephant never forgets