New to the mopar world,Need help with 318 build..pleeasse..

How could i measure the bore?at tdc the piston pretty much sits level with the deck,the man i bought it from said it had 54,000mi on rebuild,but was kinda shady about when i asked what exactly was done,thats why i ask what stock pistons look like or if they have any stampings valve reliefs,or any markings. Would the magnum block take my thumper cam i have now,or would i need a cam for the mag. Block,or should i sell all n stick to the magnum?the thumper cam is brand new,only about a month old,what i have now is 318 block,596 heads,fenderwell headers (that i made),stock 360 manifold dated 77,and a brand new 600cfm edelbrock,i do have a 650holley vac secondary carb as well,sorry for the long post just trying to get the best package,n tryin to build a nice fun street car,and something that i can smoke my neighbors falcon with...by the way thats a bad barracuda you got there...looks sick with those wheels