4 speed in A-body

Here's a pic of the clamps that you're trying to get the shifter handle past....

View attachment Pistol Grip Shifter Clamps.jpg

Put the assembly in a vise and as mentioned, use 2 long feeler gauges or very thin strips of metal to release the handle.....

View attachment Pistol Grip Shifter Slip In 004 (Small).jpg

View attachment Pistol Grip Shifter Slip In 010 (Small).jpg