All-fuel chimney: Take down and dispose of the old fuel pipe. Replace it with a new stainless steel 6" double-wall insulated component-matched chimney with a new firestop, base support, flash boot, and cap. Reconnect breeching.
Install 6" oval 316 stainless steel liner into heating flue serve one oil fired boiler with 7" breeching insulate liner with chim-mix-cap with existing crown mount multi-flue cap.
Install a chimney liner in the heating flue for one oil boiler, insulate the liner with Chim-Mix, extend the liner, install a crown-mount cap, ring the liner through the cap lid, and install a liner cap.
Install a heat flue chimney liner to serve 2 appliances: 1 gas and 1 oil, with a total input of 194000 BTUs. Install a 6" 316 Ti liner and 2 tees; gas unit to top thimble. Insulate low per NFPA 54 multi-appliance task. 6", 135 ft. Capacity: 280000 BTU/h × 80% for corrugation reduction, 224000 BTU capacity.