Assume the 509 thats in there was not degreed when installed: No, you don't have to pull the heads. You can use a spark plug style positive stop tool to find true TDC. Go slow and make sure the valve train is disconnected ( valves remain closed ) on #1 Cyl. Yes, you will have to remove the intake manifold as you will have to replace the hyd lifter with a solid lifter ( or degree checking lifter tool ) for your dial indicator to ride on. And of coarse the front of the engine will have to be open to the timing chain and gears. Just FYI, about 75% of the posts on this sight relating to cam performance issues say "advance the cam" . My personnel opinion is to stick with the cam manufacturers recommendations, unless you are a very knowledgeable engine builder and doing some fine tuning or are a cam expert. Often times you are better off purchasing the correct cam for your application rather than trying to fix an existing misapplication by advancing / retarding your cam. If you decide to advance it, I would not go over 4 degrees under most circumstances. Also, piston to valve clearance will have to be checked.