water temp guage

I just took a look at an old Mini Mania catalog and  what they have is a 
"temp guage adapter" or spacer, which screws into the head and accepts the 
capilary tube from the mechanical water temp guage.  Their part # 11K2846.  I 
am planning on getting one for when I put in a 1275 in the Bugeye. I wonder 
what people are doing with the hole in the radiator? Is it a tapered hole? 
Braze it closed? Think I'll undo the fitting tomorrow and see.  Bob C