The engine dates to 1975, heads were what was on it and had flat top pistons in it, bore was std and worn so have bored out to +30 and fitted new flat top pistons, crank was also worn but also pitted on the journals so purchased a new "eagle" crank. im not intending to build a race engine so dont need heaps of compression, and the gas we get here is unleaded and 91 or 96 octane, thanks