The #1 cylinder is at the front, nearest the radiator. Some A-C's had the timing marks on the flywheel. These are not real easy to find sometimes as they are covered with grease, oil and dirt. The simplest way to time the distributor is to find the #1 spark plug wire on the dist. cap. Then remove the #1 spark plug from the head. Place your finger over the spark plug hole and turn the engine over (by hand if possible, may require a helper). When you start to feel pressure, you're coming up on TDC. I've used a flashlight through the spark plug hole and watched the piston come up. Stop turning the engine when the piston is at top dead center and remove the dist. cap. Check the position of the rotor. If the rotor points to the #1 spark plug wire's contact, you're done. If not, loosen the hold down bolt and adjust it Untill it aligns. If you can't adjust the distributor enough, you'll have to pull it out far enough to unmesh the gears and then turn the shaft enough to align the rotor to the cap and remesh the gears. Once you get it close, turn the dist. to time correctly. Sounds complicated, but it really isn't, just tedious.
Firing order is 1243, #1 on the mag cap is the top tower nearest the eng block. Turn eng over until coming up on compression stroke on #1 cyl, to be sure remove vavle cover and when both valves are closed rotate until piston is near top, use a wire thru plug hole to find piston, on right side of torque tube where it meets block is a sight hole. As piston nears top on compression strock a line scribed on flywheel will appear in hole, usually is marked "F". This is the fire mark, the second line to appear in hole is the timig mark for distributer ignition. For the magneto us the "F" mark, center mark in hole, remove cover on magneto and turn mag backwards until points just begin to open. Install cover and be sure to line up the timing marks on the drive and driven gear in the mag cover. Check to be sure the rotor is pointed to #1 timing lug on cap-timing lug is raised mark on outside of mag cover at the 10 oclock position. Install the dist cover and wires and start the tractor.