Wow, that year had a lot of stuff on the trucks for emissions. If it is on top of the valve cover I would say it is the EGR valve, to see you emission hose routing you can see it in the tech section in the
1980 service manual, starting in section 6E-35 (page 777).
If it is the EGR valve, I do not know if you want to remove it, the EGR valve helps your car more efficiently and completely burn fuel by recirculating a portion of your exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the fuel which decreases you car's noxious emissions by prohibiting the formation of some harmful gases.
Other than that, if you don't care you can remove it and plug everything I guess, you might have a slight fuel smell from time to time from extra unburnt gases. I do know when one goes bad that it effects your engine's performance and can even make it not run.