OK I just consulted "How to Power Tune Rover V8 Engines "By Des Hammill amnd on page 32 it states
"Blocks with a daub of RED paint or numbers in the range of 2.8, 2.9 or 3.0 written on them are clearly the most desirable(4.6 litre ones)." 3MM is the thickness when the sleeve is centred.
This book is pretty authoritive and the bible for modifying Rover V8s along with teh earlier "Tuning Rover V8 engines" By David Hardcastle which I also have.
Regards Philip A

