I think this is the right place for my problem.
Had LQ9, blew rod, picked up 6.0 gto motor and put my forged internals and stock crank in the new gto block. Shop is telling me the crank for my motor is slightly longer so the flexplate and converter won't fit? trans is 4l60e

 

If it's the same crank as before how could it be longer? The only thing you changed was the block right?

 

they are saying the earlier lq9/lq4 block has longer crank?

 

That may be, but if that crank in an iron block worked just fine with your current transmission then there's no reason why it wouldn't work again just in a different block.

 

new build, never ran motor, well it started a few times and the issue came up with the flexplate not engaging so we put new flexplate in and it still has same problem

 

looks like i have to get custom converter built, other option is to replace crank

 

If it's a 99 or 2000 crank, it's .400 longer than later years. Just get a convertor built to the same length as an SBC convertor.

 

Yup. Older 6L blocks had a longer crank and require a different flexplate. I'm not sure on the converter.

Moving to trans section.