Usually, after all the bolts have been removed, the case halves come right apart.
However, sometimes they will stick together and require light tapping with a rubber mallet.

Caution should be taken around the lower run of the left case, on IH engines, as it is fragile (pretty thin at the 3 nut and bolt area). ¹⁾

If the cases are still stubborn to remove;
Light pressure applied in the transmission area followed by tapping the right case at the generator mount should work.
(not at the far end of generator mount but nearest the crankshaft as possible) ²⁾

This tool is will put 'some' pressure from within to help separate the case halves while tapping the case halves.
The tool below is basically an ironhead clutch spring compression tool (homemade) without the long standoffs. ³⁾

• Bolt it to primary gasket surface.
• Place a piece of wood inside the transmission compartment between the tool's threaded rod and the right case.
• The tool screws in against the wood and the wood puts outward pressure on the right case half.

Homemade Tool for Splitting Cases 4)

Some bolts are longer than the others.
So you'll need to keep them in order of removal for an easier time of re-installing them.
You can use a piece of cardboard or an old pizza box to keep from mixing up the primary cover screws (or cam cover).

• Make an outline on the cardboard using the new gasket or even the cover itself and poke the holes for the screws with a punch or Phillips screwdriver.
• Keeping the bolts in order as you take them off saves time and headache of remembering which length goes where.

Protecting / retaining primary cover 5) and Gearcase Cover 6) Screws

You can use an old points plate with a 1/2“X13 nut welded in the center to ease the cover off. Mount the plate inside the cover as you would normally and insert a 1/2”X13x3“ headless bolt in the center. Turn it in until the cover comes loose. This way the #2 cam stays in place so they don't all fall out when you remove the cover.

Cam Cover Removal Tool 7)