Pressurized cooling system on model A

I'm restoring a 29 AA and have a good flat tube radiator. I plan on having a pressurized cooling system, I want to use the radiator I've got. I thought about cutting about 1/2" from the existing filler neck then making an adapter in my lathe and solder it on then solder on a modern filler neck, but I dont see how to run the 5/16" tube for the over flow? Has anyone done this?
Plan B is to buy the filler neck that goes on the back side of the upper tank and solder it on, where can I buy that filler neck?
Your input would be appreciated, thanks nick c
btw I know how to solder

 

why pressurize?
A's have done well without for 80 years

 

What kind of Packing are you going to put in the Water Pump that will take any kind of Pressure? If your really set on doing this just find a Junk rad and cut the fill neck off leaving some of the top tank and set it over the stock hole and solder it on. Personally I don't think I'd make that choice.
The Wizzard

 

Yep with a stock WP it ain't gona like pressure. And the radiator won't like more than about 4psi either.

 

A stock radiator core will handle a 7 psi cap. I ran a stock radiator for years that had the filler cap soldered shut (left the flange for a dummy cap) and put the modern filler on the upper tank under the hood. This cooled a Buick V-6.