The oil pump screen is on the pick-up for the oil pump, In the parts book it is referred to as a float assembly, IH # 69 609 R91. I don't think that it really floats, but it is held just off the bottom of the oil pan. The screen prevents the oil pump from picking up bit and pieces that might otherwise get into the pump gear and cause them to fail. The bits and pieces could be from gasket pieces falling off or even bits of casting flash. Some of the sludge deposits can get to be very hard and should be prevented from entering the pump. SCREEN TO THE RESCUE.
I think that the screen is several times bigger than the minimum requirement to allow for some clogging. Be careful when cleaning the screen to not damage it or force the crud through the screen and into the oil circuit. If you poke a hole in the screen, that is a bad thing. These screens are often very brittle from years of being buffeted by the passing oil. I like to soak the crud off with gun wash that can be bought at an automotive paint store. A tooth brush that you will not likely use again is a safe scrub tool. My biker friend says that he invented the toothbrush, He suggested that I I had invented the TB, it would have been called the teeth-brush because I have all of my teeth.
In answer to the question about putting stuff on the gaskets, check with the gasket maker's instructions. More often than not, any additional goop is not required and often discouraged.
Re steering gear gasket. Make you own replacement gasket, It is easy and on You Tube.
http://youtu.be/_PY3owDijPUThis link will take you to You Tube and the rest is up to you to check around. Re sludge in the steering box. It is not very likely that there will be any sludge built up because sludge is more a waste deposit from combustion in an engine. Some of the combustion gasses pass by the piston rings and take up residence in the crankcase. The sludge is a mixture of carbon, moisture and in the old days some ethyl lead. Do yourself a big favour and wear some disposable nitrile gloves when servicing the inside parts of an old motor, because the sludge is toxic and often will contribute to cancer. They used to say that there are no old mechanics and this was the reason. The lead was a very inexpensive way to increase the octane of the fuel and it was used at the risk of the health of us all and the environment. It is often repeated by the bunk-house BS artists that the lead was there to lubricate the valves. This is not true, The lead did more to shorten the life of an engine because of the build-up that could often plug and block the passage of oiling. Ethyl lead fouled spark plugs and caused lots of carbon build-up in the combustion chamber where it contributed to a pre-ignition situation. The carbon would often become a hot spot that was heated by combustion and would ignite the air fuel mixture about the same time as the spark plug would ignite and the two flame fronts would collide and make that knocking sound. Carbon should be removed mechanically and not by doing the stupid thing of trying to blow it out under hard acceleration. The blow-it-out attempt does not work and will often glaze the carbon deposit and make the situation much worse. It may be possible to remove the carbon deposit build-up, if there is any, by going for a nice highway drive for several hours. Take it easy and do not do anything heroic. I have seen additives flushed down the carburetor while producing huge clouds of smoky exhaust. That may have been all that happened. . Just take it easy. Revving the p... out of the motor will not tune it up and fix a problem.