I drilled and tapped the top neck piece for a 1/8 npt fitting, see pictures. This was very easy, you just have to be careful to put the hole in the right spot so the cap clears the fitting and so the fitting stays above the bottom seat for the radiator cap. And you can only screw in the fitting a few threads so that it does not poke into the neck and interfere with the radiator cap, so don't screw in the 1/8 tap too far which would enlarge the hole more and require the fitting to have to be screwed in too far. Take small steps and remember the fitting doesn't have to be super tight because it won't be under pressure, the teflon tape will seal it. I was able to screw it in a few turns and get the fitting pointing downwards for the hose to attach, it was tight enough and it worked out good.

Then I used my dremel to cut off the hose nipple for the hose that would go from the thermostat cover to the ast, then I grinded down the remaining part of the nipple sticking out, then I drilled and tapped it for a 1/8 npt pipe plug. Drilling it didn't remove all of the nipple inside the hole, but while tapping it the nipple came loose and I unscrewed sections of it out of the hole.

The hose coming off the bottom of the radiator that would go to the bottom of the ast, I cut it and clamped in a bolt which I cut off the threaded part first.

This cost me nothing because I had the extra pipe fittings already and the drill and tap. I did this to get rid of my aluminum AST, which after reading lots of debate on the subject I think it's not needed, and to clean up the engine bay a little. I used my Lisle 24610 Spill-Free Funnel to let the car run for a while and get the air bubbles out. Took it for a test drive, so far so good, no leaks.

I used teflon tape on the pipe fittings. And a 13 psi radiator cap, either 10227 or 10327.

 

Archive Worthy imho with other AST removal related info. Thank you for sharing.

 

That's how mine is



Now being converted to -4AN