Excluding the crank as they are not a weak point, you can buy rods for 400 and pistons for 500 rough figures.

Machining will be needed and a full set of brarings and oil/water pumps etc.

See Matt Lewis for most of the bits

See here for conrods.....

http://cgi.ebay.co.uk/H-Beam-Conrods...QQcmdZViewItem