To find tdc: if you have an early head, get an old spark plug, remove the innards and weld I a bit of round bar so that when the plug is screwed in the bar protrudes a little into the bore. Maybe 1/2 inch. When fitted rotate the engine gently until the piston contacts the bar. Mark that position. Wind the engine back until it goes chock in the other direction. Mark that position. TDC is half way between the two. If you don’t have an early head the same principle applies, just improvise.
Alan Fairless