clove100:
Welcome to the conversation!
First of all, when you get your keg, don't cut the top at all! The existing hole should line up perfectly with the flange you buy. Just remove the sanke valve. You probably knew this already but I wanted to make sure.
For the tri-clamp ,order from
http://www.brewhaus.com/Tri_Clamp_2in_Clamp_p/30001665.htm or
http://milehidistilling.900footalien.com/connectors.htm I believe you are correct in your assumption that you can silver solder the flange to the column, and use that to clamp to the keg, however I have never done this personally so take that into consideration. To be honest I ordered my column ,stainless steel, prebuilt so I didn't have to mess with soldering the flange or anything else, however my mentor, who built a copper column did this:
attached
Others have more experience with this than I do so I will defer to them.
Also don't forget to order the rubber o-ring gasket at the same time. I actually ordered 5 gaskets so I have extras when I lose/damage them ,hey they are cheap, order them at the same time you order your clamps and flange and save on shipping,.
That was a good price on the reostat. You might want to share the web site where you bought it. If you have a pipe or plumbing supply store in your town they should be able to order the bushings for you if you can't order them from McJunkin Corp online.
I'm with you on what a pain it is monitoring a flame. That's why I am a big advocate of the electric coil. So far I haven't heard of anyone yet that has been blown across anywhere using the eletric system. My mentor who uses propane had a leak that ran down the side of his column and keg then caught on fire running all the way back up his keg and column. Luckily he got it out before his garage went up. I also really like the way the coil is REALLY quiet. Just set it and forget it.
What system do you use to cool your condenser?
Good luck and let us know your progress as you go along.