There is a company called Imperial Services that will convert your pushbuttons to work with a later trans, but it's pricey $$$!! However this really opens up your transmission choices over the 64-65 pushbutton v8 904's. I went with an aftermarket floor shifter when I did the same swap you are doing, it was the quickest and easiest solution although I'd like to return to the pushbuttons at some point, just trying to weigh the cost and time of finding a 65 trans (only year for PB's and slip-yoke) vs sending in the typewriter to Imperial. Luckily I have an extra button shifter and I've looked long and hard at it but can't figure out how they convert it. No pics are readily available online of a converted shifter, either, at least that I've (not) found.
One place I've thought to look as a donor is a 64-65 A-100 van. They came with small-block 727's and I *think* that 64-65 vans came with a two-cable auto shifter (neatly mounted on the dash!).
