The first panel up towards the dash after the floor pans, at an angle and where steering rack bolts to floor without any brackets or fittings, see also same panel with steering rack fitting AHA36006
for 1976 on rubber mounted subframe or ALA6602 for pre 1976. Heritage use them on their Clubman shells but require modification and insets. This is the bare panel only i.e. no steering rack mounts etc.