Do you need another pump? If your coal boiler with 1-1/2" tappings was right next to the existing boiler I would say no. But when you add the 60' supply, 60' return and the associated elbows and valves you will increase the piping resistance. Especially if you use less than 1-1/2 inch copper piping. The additional piping resistance will move the pump operating point and reduce the flow rate. Will it matter? Maybe not, but I'd plan for an additional pump in my piping layout. The additional pump would need to run whenever any of your existing pumps are running. Easily done if you have pump relays like the Honeywell R845. Have you had any problems with heat distribution in the zones, trapped air preventing flow, excessive water flow noise, using a lot of make up water? If yes now would be the time to make corrections.