Folks please notice this "want-ad" was originally posted in October 2016. GT4 Peter may no longer be in the market for a damper.
The old Boss dampers certainly have extreme value to owners and restorers of R code equipped Mustangs. BUT due to the rubber in its construction any damper more than 20 years old cannot be trusted to perform at the level it was originally designed to perform at. AND the timing marks on an unbonded 20 year old damper cannot be trusted for timing an engine either (the R code engines were the only 335 series engines equipped with fully bonded dampers).
If anyone is in the market for a NEW damper for a high performance 335 series engine you may want to consider PowerBond's p.n. PB1082SS “fully bonded” steel race damper; made in Australia, SFI approved. $215 at Summit Racing … available for shipping today as they say.