I was going to use the flywheel from my 305 on the 350 but I see some of the teeth are broken. Was looking at new ones from autozone, they have one listed without a weight and one with. do i need a weight on my flywheel? or is what i'm reading on google right, (350's were internal balanced until 86. 86 and newer are external balanced.)

 

I honestly did not know they ever externally balanced a 350 smallblock Chev. As for weights; it depends on what thw eight is for. If it's to make up for internal balancing, then it's needed on any engine that's externally balanced.
I have seen flywheels that had weight or holes drilled to balance, but were for internally balanced SBC. Guess you need to ask them the purpose of the weights, and see if your engine is internally balanced or not.

 

The only externally balanced small block I am aware of is the 400 inch small block.

 

The later ones do have a weight on the flywheel. I bought one for my 76 Nova without knowing the difference. I went a good month like that I just new something wasn't right I could no longer see out of the rear view mirror. I put it in because mt ring gear was toast too.

Here is what I did. I went to NAPA and got a new ring gear. About 10 bucks at the time. Place the flywheel on 4x4 or something. As long as its shorter than the flywheel is. With a propane torch heat the ring up evenly all the way around. Don't get it red hot or turn it blue, just get it as hot as you can without doing that. The ring should drop right off. Remember to NOT heat the flywheel or they will expand together and it will get you no where. Now heat the new ring up slowly and evenly. You can put the flywheel in the freezer or a snow bank if you like. Then when the flywheel is cold and ring is hot it will slip right on. I would do this on a nice flat concrete floor or a good steel work bench. Just be sure its good and flat. They don't have to be precisely installed just don't have it all cockeyed.

As my grandpa (he taught me this) says, Easy Peasy Japaneasy.