Yes, thats what I did. Its silver soldered. I was afraid of blowing up with the old tank so i filled it full of water and used a grinder to cut the old neck out and an inch or so around the neck of the tank itself. I then put it on the bench vise and heated it up and pulled it out.
I brought the new GN tank and old GM GP neck to a local rad shop and paid them $20 to solder it.
My first truck, an '88 Chebby, suffered from a leaky rotted tank. After I replaced the tank I tried lighting the old one up but, with 1/8 of a tank, it wouldn't go. I'm guessing there was no oxygen in there to support combustion. Probably for the best.