Can you just get a plug for this hole on a desmogged 78? Has anyone done this. Also searched and could not find a direct replacement. Could this work for me?
http://shop.hoseandfittings.com/cat..._&_Washers/MMetric_Hex_Plug/4030M-16x1.5.html
http://shop.hoseandfittings.com/cat..._&_Washers/MMetric_Hex_Plug/4030M-16x1.5.html