i had the same problem and i bought another radiator from ebay and
while putting that radiator in i let my son tighten the clamp on the niple leading to the resevor and we broke it off.... i went to autozone and they had a universal vacuum connector with flares on each end... i popped it into the whole and it works perfectly no expoy or anything.... and i leaks probably a tablespoon a month....

plus, the neck brake your talking about occurs from preasure so i hope this little 2 dollar thing will pop out instead of my neck breaking on the radiator...