Piping of Mulitiple Boilers

Leatherneck

My question is I looked at a large residential heating system and discovered multiple boilers had been piped. Old system originally had hand fired coal/oil burner for steam (two pipe). Then it appears that natural gas became available and 2 gas boilers were added. A 2" nipple was added to the original steam riser (welded in) and the original boiler had a Hartford Loop, 2d new gas boilers just used a check valve on the return. (Now just to verify my thoughts) The original boiler is not in use but is still piped in the system. The operating boiler comes on and you can feel the old coal fired boiler heat up. The Hartford Loop is still in the Header Return (Original Boiler) and the operating Boiler like I said has a Check Valve on the return. No Equalizers on the the Operating Boiler which has a 2d boiler piped in parallel but it to does not fire(Just sits there piped in the system). My thought is disconnect the old Original Coal Boiler and get it out of the piping system. Then 2dly get the 2 boilers that are piped in parallel, operating instead of having just one operate. There are no valves to isolate these two. Or if the load doesn't warrant two, do I just valve off the one and operate on 1? They are both the same size. Input 220,000 Output 180,000. Big old House (Historical Type 3 floors). One radiator had a valve settings Vapor/Vacumn, hand valve? 2 Pipe system. Any thoughts appreciated.