Woody... It depends whether the cylinder is on compression at TDC. Here both valves will be closed, followers on the back of the cam. Both push rods down. As long as the camshaft is located to the drive gear with the key in place and the timing gears are correct for your engine with the timing marks lined up OK, the job's a good 'un. Crank pinion also locates with a key so is fixed in relation to the crank.
Recheck the magneto timing while the head is still off....easy to measure piston height before TDC.
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Swarfy.