Timing a 10-20

I am getting ready to try to start my 10-20 but cannot locate the "Timing Hole." I can locate the "DC" mark on the flywheel but it is out of sight when the #1 piston is at/near TDC.
Any other way to locate TDC? Any additional advice on timing with an E4A mag?

locate TDC by putting thumb over plug hole then crank till you feel compression pushing out. then use a pop straw or piece of wire and crank slowly till you can feel piston coming to tdc.
when i have the valve cover off i just watch the running mate #4 cyl. so that the rockers are on the rock and you know #1 is on compression.

Rustred pretty well nailed it. Here is some step-by-step detail

take #1 plug out, and loosen the other 3 to help reduce compression which makes the engine easier to turn over by hand. It is best to have a helper with the next part. Place thumb over #1 spark plug hole, or use a compression guage while slowly turning the engine. When #1 is coming up on the compression stroke, stop turning. get a solid piece of wire or a straw or something that is 10-12 inches long, and place into #1 plug hole until it bottoms out. I keep a 1/8" wooden dowl rod in the tool box to do this. Now slowly start to crank the engine again, and when the wire/straw is at the top of the stroke, STOP. Better yet, go a whisker past, and then back the engine up, and determine where absolute TDC is.

Now that you have done that, take your mag (doesn't matter what kind), and rotate it with the distributor cap off until the rotor is just about to make contact where the #1 pickup is on the dist cap. You should also have the point cover off, and double check that the points are JUST beginning to open.

Now, on the govenor coupling disk, see if the tabs are in correct alignment to match up to the mag. If not, take out the 2 small bolts and rotate the coupling disk until it is in correct orientation to match up to the slots/tabs on the magneto. Re-install the 2 small bolts in the holes that maintain the correct alignment. NOTE! the bolts may not end up in the same holes where they originally were. They probably will if the tractor was correctly timed to begin with. BUT, it doesn't matter what holes they go in, what matters is that the coupling disk is in the correct orientation.

once those bolts are in and snug, bolt up the magneto. re-install #1 plug, and tighten the other 3. replace plug wires, in the correct 1,3,4,2 firing order.

You are now timed without have to look at any timing marks or the valve train. This technique applies to all F-series tractors and either the E4A or F4 magnetos (and Bosch and others).