I think this is the info on modifying a bridge. I saved this six years ago in case I may need it. It's for the bascule bridge, but you could modify the dimensions for the 213. Hope this helps.
Rejuvenating A Bascule Bridge
The Lionel Bascule Bridge #313 has long ago been sidelined on most layouts because of its low 4 5/8” clearance. Consists with schnables, stack cars, and now the acela with its high pantograph must be rerouted around it! However, it is felt that the uniqueness of the bascule bridge is simply not captured by any other bridge offerings by O gauge manufacturers. The question then becomes how to increase the clearance while maintaining the basic “look” of a bascule bridge? While there is only one option for increasing clearance on the arm of the bridge, we can either raise the towers or put the whole base of the bridge on two abutments and drop the track down between the abutments. After reviewing pictures of rail bridges on the internet, I found a number resting on large abutments with track running between the abutments. This approach is used for modifying the 313 bascule bridge. A clearance of 5 13/16” was selected as a compromise between maintaining the bascule “look”, allowing use with modern cars, and construction ease. The picture below shows the final product. ￼
The rejuvenation involves inserting two wooden abutments under the towers of the bridge, cutting out the track between the towers and lowering it to the bottom of the abutments. One must also lower the plastic track bed on the moving arm of the bridge by inserting wood strips. The following pcture shows the 2 wood strips and the two abutments attached to a stabilizing ½” board. ￼
The tools needed to do this job are a reciprocating saw with a 7” 8/12 TPI blade, a table or radial saw for ripping the strips of wood, a drill, clamps, and glue. Also required are assorted screws , plywood scraps and a ½” clear pine board 16 “ long( ½ X 3 X 24” hobby lumber is available at many stores).
The first step is to remove the feet and plastic from the bottom of the bridge base. Then use the bridge base as a pattern for making the two wooden abutments. Keep in mind that the bridge arm must have a recess in the abutments when it closes. The wooden abutments need to be 1 3/8” thick. Gluing and clamping a ¾” and a 5/8” piece of plywood together will produce the desired thickness. These pieces should not be less than 1 3/8” or the moving arm on the bridge will not close. Be sure to cut holes for the electrical connections under the bridge house and the track.
Connect the base to the abutments with four 1 7/8” #8 round headed screws by drilling two holes through the base near each tower. The regular holes in the base are too close to the edge of the abutment to offer much holding power when you saw out the metal center track section of the bridge. The regular holes can later be used to screw down the bridge on your layout.
To keep the two towers in precise alignment while the center of the bridge base is sawed out, glue or screw a ½” piece of plywood on the bottom of the two wood abutments attached under the towers. The abutments plus the connecting ½” plywood were shown earlier. Now mark where you will cut to remove the center section of the bridge base. Place a straight edge along the inside edge of the metal bridge arm and draw a line on the base. The following picture shows where the cut was made and final lowering and alignment of the center track. Keep in mind that train cars must pass through this cut. ￼
Next clamp the bridge to your workbench and remove the plastic track bed from the bottom of the metal bridge arm. Then run the bridge arm up so that the saw blade will not hit it. Using a reciprocating saw with a 7” 8/12 TPI blade, cut out the centerpiece of the bridge base. Run the reciprocating saw at a high speed when cutting. Shorter or coarser blades can create control problems! Sand and paint cuts with Model Master 36320.
Now rip two strips of wood to insert between the plastic track bed and the medal bridge arm. These are shown in final form in the second picture above. Each should be 1 3/16 x 7/16 x 16. Using the bridge arm as a pattern mark where the holes should be drilled in the wood strips to reassemble the parts. Drill holes slightly larger than the 1 5/8” #8 round headed screws needed to connect the bridge arm and the strips to the plastic track bed. Note that a recess must be cut in each strip to accommodate the two bumps in each side of the plastic bed. Prime and then spray paint the strips using model master 34079 (dark green) and FS 37038 (flat black) in equal parts covered with semi-gloss lacquer over coat. The following picture shows the inserted strips on the bridge arm.
Those of you who don’t want the stabilizing ½ “ plywood on the bottom of the bridge can carefully remove it and put the bridge directly on your layout.
Finally four holes are drilled in the corners of the track cut out of the center of the bridge base. See the earlier picture. Line up the track with the track on the bridge arm and carefully drill screw holes. Washers can then be used to adjust the height of this section of track with respect to the track on the bridge arm when it is lowered. Clearly, the bridge clearance can be made larger than 5 13/16 by increasing the thickness of the pieces shown in second picture. Aside from finding thicker wood, I feel this will further alter the bridges bascule look. If you have comments or questions, email me at: firstname.lastname@example.org