push button ignition

...............Well..................there's about a thousand ways to do this.................

1--The obvious, get a different column, IE a 70/ later column and keep the column mounted ignition

2--"actuall keyed ignition on the dash", you say. Well if you do NOT do this, what WILL you do? In many states, it is illegal to leave keys in the ignition, IE if you don't have some sort of lock, you cannot protect the car from theft, and may open yourself to liability. Some kid steals the car, wrecks the car and injures someone, maybe themselves, and a smart lawyer realizes you MADE the car easy to steal because there's no lock. Hope you have a lawyer.

3--Some sort of hidden push button/ toggle/ latching relay, but this does not address the "accessory" issue

4--Adapt an aftermarket antitheft system which disables the fuel pump/ ignition/ etc

5--Figure out a way to construct a mount for a switch in the dash.

Option "1" seems like the way out, to me.