Why does my 9" Lockup require Transmission Mod?

[tomcatturbo]

Hi All

I have a new 9" 3400 Lockup Converter from Fuddle Racing, and I heard that my transmission is going to also require some modifying to use this convertor.

Can anybody explain what all this is, and approximately how much $ this is going to cost approximately?

I think I heard my valve body is going to require some modification, etc?

Thanks for the advice and heads up