Just put these out on E-Bay. ( 7 available ATM)
Racing Beat 3" Big Bore Pre Silencer Boxes thick Stainless Steel . Condition is New. but old stock and never used Body is 13" long and 5" wide (Made in America)
This Power Pulse Pre-Silencer was designed for the intense heat of Rotary Engines and is manufactured in quality 304 Stainless Steel.
This straight through unpacked pre silencer is designed to gut down high frequency pitch by allowing exhaust gasses to expand into the silencer box
https://www.ebay.co.uk/itm/Racing-Beat-3-Big-Bore-Pre-Silencer-Boxes-thick-Stainless-Steel/254368487602?hash=item3b398b18b2:g:xBUAAOSwljVdhldM