The originals are made from cast "pot metal" and do corrode and often break off in the T-stat housing. The Dutchman can be removed & the threads chased (1/2" MNPT) and a new nipple installed.
This is the only photo I have handy. The ones we stock are cad plated steel.
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Jerry Downey
JERRYS LT5 GASKETS & PARTS
http://www.jerrysgaskets.com
1994
ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc.
2016 Black-Red, 3LT-Z51 Auto 8-speed.