If I recall correctly the alloy fabrication and welding was a couple hundred. I sent them the alloy materials including cap and threaded fitting bungs. A local welder did the stainless tubes to the stainless pipe thread/AN adaptor welding. (3/8 NPT male to AN-8 male). Then there was AN hardware and new hose, plus the powder coating... so somewhere around $500 all in for the conversion.
There are weld it yourself 6" diameter alloy tank kits sold on ebay with thin walls and no fittings for about a hundred, btw.
