First thing you need is a piece of plate 6 inches in diameter. The thicker the better, but around 16 - 20 mm thick is good.
You will also need a 2 1/2" X 1" UNF bolt and nut, and three 3" X 3/8" UNF bolts.
The bolt holes in the flywheel are 3/8 UNF thread on a 4" PCD (same as the wheel studs). If you remember your high school geometry, you will know how to set them out.
If you have forgotten, then set your calipers at 2" and draw a circle around the centre. Now leaving your calipers at 2", draw radii around the circle and centre punch every second line.
Drill the outside holes 3/8", and the centre hole 1". The polished finish is optional.
Now weld the nut in the centre, using the bolt to pull it down square. Chamfer the sides of the nut to get a good weld. Use a stick welder or a good MIG - there will be a lot of pressure on here!
I used two passes just to be sure.
Next you need to make a plug to go in the end of the crank for the 1" bolt to push on. Don't push on the flywheel bolt - you may damage the bolt or your crank.
Make the outer diameter to suit the hole in the flywheel - 1 3/8", and the pin to suit the crank hole - 1/2". If you don't have access to a lathe, you could use a cheap 1/2" bolt and a thick flat washer. But whatever you do - don't push directly on the end of the crank!
Here it is installed.
I also like to turn the end of the 1" bolt off square - have a look and you'll see why!
Now you can bolt the puller up. Make sure you have plenty of bolt threaded into the flywheel. Snapping a bolt is no problem, but ripping the thread out is! The holes are quite deep, well over an inch. Also make sure the puller is perfectly square with the flywheel - measure it if you are not sure or use a spacer.
Below you can see the pusher piece in place. Oil all the threads before use.
This setup should be around 1" shorter than the standard wok cover and overthrow nuts, so should fit easily with the engine installed. For more clearance, use a 2" long pusher bolt, or weld the nut into the centre of the plate.
If you aren't confident of your welding abilities and have the engine out with plenty of room, you can flip the puller so the nut is on the inside. You will need to swap the three 3" bolts for 4" ones.
If the flywheel won't come, leave it overnight with pressure on. Next step is to add some heat to it - sometimes a paint stripping gun is enough.