Thermostat and Water Pump Housing Corrosion Pit Repair

How do you fix a badly pitted engine coolant housing to keep it from leaking by the coolant hose? Kent had to deal with a bad thermostat housing on his W113 280SL. This problem is common on a lot of older Mercedes engines both gas and diesel.
The models included will be:
1950’s models 170D, 180D, 190, 190d, 220, 220S, 220SE. 1960’s models W111 220S, 220SE, 220Seb, 250SE and 280SE, W110 models 190d, 200D, 200 and 230, W113 models 230SL, 250SL, and 280SL, W108 models 250S, 250SE, 280S, 280SE and 280SEL, W109 models 300SEL, 3.5, 4.5 and 6.3, R107 models 350SL and 450SL, W114 W115 models 220, 230, 250, 250C, 280, 280C, 220D and 240D and early W116 models 280S, 280SE, 450SE and 450SEL
Late W114 and W115 Chassis Sedans and Coupes: Mercedes 280, Mercedes 280C, Mercedes 240D, Mercedes 300D.
Late W116 Sedans: Mercedes 280SE, Mercedes 280SEL, Mercedes 300SD, Mercedes 450SE, Mercedes 450SEL and Mercedes 450SEL 6.9.
All W123 Chassis Sedans, Coupes and Wagons: Mercedes 240D, Mercedes 300D, Mercedes 300CD, Mercedes 300TD, Mercedes 230E, Mercedes 280E, Mercedes 280CE, Mercedes 280TE.
All 126 Chassis Sedans and Coupes 1981 to 1991: Mercedes 300SD, Mercedes 300SDL, Mercedes 300SE, Mercedes 300SEL, Mercedes 350SD, Mercedes 350SDL, Mercedes 380SE, Mercedes 380SEC, Mercedes 380SEL, Mercedes 420SEL, Mercedes 500SEC, Mercedes 500SEL, Mercedes 560SEC, Mercedes 560SEL.
All W201 Chassis Sedans: Mercedes 190D 2.5, Mercedes 190D 2.5, Mercedes 190E 2.3, Mercedes 190E 2.3 16V, Mercedes 190E 2.6.
All W124 Sedans, Coupes and Wagons: Mercedes 260E, Mercedes 300E, Mercedes 300D, Mercedes 300TD, Mercedes 300TE, Mercedes 300CE, Mercedes 400E, Mercedes 500E, Mercedes E320, Mercedes E420, Mercedes CE320, Mercedes E300D