This is the process I was thinking.
1 - cut the head tube in the middle
2 - put the front of the frame in my forge or heat enough with torch to dislodge the lugs and do the same to the portion of the headtube left in the lugs
3 - clean clean clean
4 - cut and notch top tube and down tube approximately 3 cm
5 - fit components in a jig to keep the headtube in line with the seat tube
6 - tack in place let cool and check for alignment when released from jig
7 - re braze parts
8 - face the new head tube, send for chrome, re paint and build

The lugs have the angle built into them so shortening the two tubes will only cause the headtube to be longer and from my thinking the only change in geometry will be a non horizontal top tube and a slightly higher handlebar height (and of course shorter top and down tubes) This is not a bad thing as I am going on to 50 years old and not as limber as I once was. Keeping the rest of the bike intact insures that everything else should be in good alignment and a simple jig would be all that is needed to make the main triangle straight.

I have a old Bianchi that I don't really care about that I may experiment on first. I am sure of my abilities but this is old 531 and nervex lugs and quite concerned about ruining it. I realize that I could dismantle the whole front triangle and rebuild to properly size the bike but I was hoping to do the least destructive method.