Mainly so I can replace the bearings and get the block acid dipped ready for spraying

Over bore to 1.9 you'll regret it if you don't, quicker spool for a laggy turbo if you choose that route in the future. Standard pistons are not fully forged but ok up to around 400 by the looks of things. I would replace them too, as Elliott says no price difference in the different sized pistons.