Does anyone know the volume (cc) of the combustion chamber of an 18R cylinder head?

I'm planning on doing a stock rebuild for an 18R from a RN46 Hilux. Haven't pulled out the engine yet, but thinking about getting either 40th or 60th pistons. I was thinking if I go 60th I could raise the compression ratio too much. I've got a 3TC that had 1mm oversized pistons, with 1mm shaved head and stock cam, and that pinged. I had to run it on 98 octane with spark plugs two heat ranges colder (NGK BP5EY -> BP7EY).

Anyone know the stock 18R camshaft specs? I can work out the dynamic compression ratio.