I am a little late coming to this party. I do not get to spend too much time on the forum these days.
I also have the Bowser 32" table. I purchased it a long time ago, back when all that was available was the Bowser or Diamond Scale. Regardless, here is what I did to mine 8 years ago and it still functions great today.
You already stated that you have an upgraded drive. That is good, the original plywood wheel and rubber tire setup from Bowser was very weak for such a large table. You also commented you wanted to get more weight on the boogie wheels.
As you know, those wheels are no longer available. For me, I supported the whole bridge assembly on the base of a 12VDC antenna rotor motor. This would be for anybody that still has an antenna on their home. It operates at 12VDC and only turns 5RPM at very low speeds. I control it with an old MRC power supply and since it can turn so slowly, I never even needed an indexing kit. I can line it up by eye everytime. As the pics show, the bridge fully supports and can easily and slowly turn even my scale UP Challenger.
The Bowser plastic bridge is screwed to a milled block of wood that runs the full length of the bridge. All the weight of the engine is carried on the center bearing shaft of the motor. All I use the boogie wheels for is electrical pickup and as long as one of the four is touching the rail, I am good to go. The other track lead is connected directly to the rotor base.
I had to tweak the centerline point of the pit to make the bridge swing clearly 360 degrees. You may need to trim some of the bridge to clear any tight spots.
If you look at my pics, you can see the three screws I used each side to hold the bridge to the rotor. You can also see the base of the rotor motor in the pit. I never painted it and I think it looks just fine.
Hope that helps a little. Those old Bowsers are certainly a little difficult to get working correctly. On my next layout, I will be budgeting for a Millhouse or ROSS model.
Finally, if you have the OGR magazines from last year, look for my layout that was featured in the February / March issue 2012. There should be another pic or two.