The battery box is mounted with rubber bushings.
Take a pry bar against the back of the tranny and pry the box backward to get clearance to drop the bowl.

I just looked at this old thread, and realized I never updated it to the final results.

In the end I used a #50 pilot and a #150 main, and the cure for the lean surge just off idle was to remove one of the three washers under the needle clip....so I only had 2 washers below the needle.

It is my belief you should choose a pilot jet that allows you to have the smoothest engine idle with the mixture screw somewhere between 1.5 - 2 turns out.  If the best idle smoothness occurs at more than 2 turns out you need to install a larger pilot jet, and if your screw is less than 1.5 turns out and you can turn the screw almost all the way in and the engine still runs - you need a smaller pilot jet.  The pilot jet size should not be selected based on backfire issues or random guesses....adjust the idle fuel mixture as shown in the video I linked below.....the pilot jet size should be selected for a good idle mixture with the screw between 1.5 to 2 turns out.  The main jet should be selected for a good smooth acceleration at full throttle....and the needle washers should be used to adjust the mixture from just off idle to about 1/4 throttle.

Use the method in the following video to adjust your idle mixture.

https://www.youtube.com/watch?v=YxpQjDQzX7g