Thanks
pbonsalb and
bigjae1976. A bit of a delayed reply but I read your comments when you posted them and took them onboard and they had me rethinking solid mounts and, instead, considering something more compliant.
I had found these:
AKG $350+$75, 95A poly
https://www.akgmotorsport.com/produc...8x-e9x-non-m3/
https://www.akgmotorsport.com/produc...e92-e93-z3-z4/
(but could leave off the cups)
034 Motorsport $196+$50, 50-60A rubber
https://store.034motorsport.com/moto...2-n54-n55.html
https://store.034motorsport.com/moto...nger-side.html
https://store.034motorsport.com/tran...-line-bmw.html
BMW OE $32-45, __A (? durometer) rubber
E46 M3 trans mounts
The AGK mounts are poly and there have been a number of people on the N5X platform that have experienced issues with these mounts since the turbo is tucked away down the right-hand side near the mount and they become affected by the heat.
The 034 mounts are rubber but a softer mount. I've also read of issues on the N5X platform when they fail (fall apart) after a very short period (less than 1000kms!).
I was thinking 80A +/-10A would be suitable but haven't found anything in that range yet - the above were the closest that I've found so far.
The OEM E46 trans mount is another option but I haven't found any information on its hardness rating.