4-speed shifter question......

We are in the process of converting our '76 Dart to a four speed. This is the first 4-speed conversion we've done, so I am wondering....

We have a bayonet style A-body shifter and need to get the clip and rubber isolator. Is there a reason we couldn't just slide the handle into the shifter and use shim stock to take up the space between the handle and the shifter base slot....then auger two holes into the base and bolt the it all together?

Here's a pic my husband made up so we are all on the same page, lol...