Would using lead weights be a bad idea for anchoring a piece of drift wood?

I certainly wouldn't be using lead in your aquarium. Why do you think you need to anchor down your wood? once the wood becomes saturated with water it normally stays where it is.

Lead is extremely poisonous for fish in general, but lethal to Plecos.
Boiling the wood for some hours will make it sink as well.
You can imagine i got quite a big pan

i usually drill a hole into a piece of slate, then using a stainless steel screw, screw the slate to the driftwood. then i bury the slate under the substrate in my tank. this secures the driftwood into position and keeps it there reguarless of the oscars attempts to move it.

x2 on the slate and stainless screw. I wouldnt use lead

never use lead mate

yeah i figured lead was a bad idea just thought i would check with OFL

A large lead weight would be a bad idea. Soak your bog wood in a large container with a big weight on it. It shouldnt be floating after a week. Then add it to the tank