Is this true? He told me that I would have to replace the Flywheel???? WTF is up with that? Any thoughts?

If you are installing the TH400 torque converter it will use a larger bolt up pattern. You can redrill the flex plate for the new pattern if you want, otherwise you will need to get a new flex plate.

My whole lower assembly was balanced Wont a new Flex plate screw that up?

Interesting...

I just installed my TH400 and used my 700R4 flexplate... bolted right up..

Rick

If yours is balanced, then redrill your flexplate.

Just use a TH350 torque converter. It will fit on the TH400 and have the smaller bolt pattern for the flexplate.

It could be just as easy to replace the flexplate. Most aftermarket ones will have a dual bolt pattern.