OK, I have been doing research trying to find an adapter plate for my turbo 400 to my recently acquired LQ4. I see on advance adapters site that they say the 6.0L iron block will not work?? But I see on some peoples sigs and other posts that some have a turbo 400 behind an iron block LS engine?? Can someone with a TH350/400 behind an iron block explain this and tell me where I can find an adapter please.

 

I think what you need to figure out is if the LQ4 has a long type crank or not and then you can see what you need.
a long Crank needs a flat flexplate and a regular Th400 TC to mate it to the trans.
the other type needs a spacer in the crank to get it to fit.
look at the sticky in the automatic trans section for some more infirmation. i have a LQ4 that will have TH350 Mated to it. it is possible.

 

I have a lq4 block and a P.B t400 and a tci sfi flex plate and it matched up perfect.