SHIFTWORKS sells conversion kits, parts and accessories to convert 1964-81 General Motors factory automatic (Powerglide and TH) console shifters for use with Turbo Hydramatic and Overdrive transmissions.
They say:
Now you can retain that original factory LOOK and still upgrade your transmission. Whether you want to replace your Powerglide with a TH350 or TH400 transmission or upgrade to an overdrive transmission like the TH200-4R, TH700-R4, or the 4L60, you can keep your original factory shifter! Shiftworks kits allow you to modify the shifter to function properly with different transmissions.