where can i get em?, how much?

what kind of welder to put em on, and what is inclued, as it looks to methat the very back of the sill is actually part of the rear quarter, how would i go about replacing this bit?, and the very front of the sill is indented in slightly, does the new sills have this part?

haven't seen a replacement sill before , we have had ours made by a sheet metal guy/plumber and panelbeater/sponsor fitted them and yes they are part of the rer quarters thats y he did it not us , also made new ones from a thicker steel

i know one member has got them before from a place in queensland, cant remember details, just wondering if anyone knew of other places, and answers to my other questions mainly, thanks mate