If you find it difficult to R&R the plugs, you could do just as well for flushing the block by connecting a water hose (adapt to heater or radiator hoses using iron pipe fittings) from your house system. To be safe, put an adjustable pressure regulator set to 18 psi in line with the hose, especially if the radiator and heater core are still connected.
With thermostat removed, flush all circuits and components (water pump, block, reservoir, and heater core) with full flow for 3 or 4 minutes in both directions for best effect.
When done, pour 3 or 4 gallons of distilled water ($1 a gallon at grocery store) thru everything (again, in both directions) to displace 90+% of the tap water with distilled, then drain out what you can from radiator and block with lower radiator hose disconnected, install thermostat (after testing for proper opening and closing in pan of water on stove with thermometer), add 1/2 system capacity (9.4/2 = 4.7 qts.) of 100% G05 antifreeze in your brand of choice (Zerex G05 - yellow, Chrysler/Mopar 5 Year/100kMile 68048953AB MS-9769 - reddish, or Ford/Motorcraft VC-7-B - yellow), and top off remaining space with distilled water using FSM fill and bleed procedure.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs