Those are called rivets which are extremely durable and strong when installed correctly using a rivet gun, however, standard stainless bolts and nuts sourced from a local hardware store will work just as well.
Just bourght a Detroit bypass valve from Outmotoring.
Managed to track delivery,which was usefull.
Fitted it yesterday,a,great improvement no more yo-yo and better acceleration too.
Very pleased thanks.
Would recommend Outmotoring to anyone,thinking of buying parts for their mini.
graham Kirkland
Aaron has been superior in customer service each and every time!
Daniel Hanscome
I ordered a part that I did not end up needed - They took the return and were very responsive to all my requests - Great company