bought a replacement B&M flexplate to replace stock. Is it critical to balance the flex plate with the engine or can I just bolt it on. I know it comes balance by itself from the factory but I'm not sure it the stock flex plate was balance with the engine or not.

 

Should be a direct bolt on as long as its the right one for your app.

 

thats what I figured

 

The only SB flexplates that require any balancing are 400's.