Depending on how much work (I.E. money) you are going to put into the engine will determine if you need 24's.
From what it sounds like they may be a good idea once you are finished.
Boring it 1mm = 3.04L vs 2.97L
Rick is talking about boring the stock liners. Minimal machining.
The block can be bored larger but the cost for such would be very steep for the minor gains (comparably)
However even boring the engine out 5mm (roughly the max estimated limit) would only net you 3.3L
You would have to machine out the cast in liners and then have a set of new liners pressed in. Also depending on the availability of liner diameter the price could get very expensive.
Also the thinner you make the cylinder walls the weaker the block's strutural integrity is.
