im doing rebuild on mine and im just wondering what and where is the best place to renew the bolts that hold the two halves of the block together, but its the ones in the water ways beside the piston chanbers, as idealy i want to replace them as wouldnt want them to leek in any way,

 

Unless the bolts are corroded, normally you just change the dowty seals under the bolt head only, but check there is'nt any corrosion in that area where they seal.
I use a small amount of Wellseal on the bolt underhead & sealing surface on the block to make sure, never had a leak to date.