Is there any way of increasing the seat adjustment on and 04 JDM. I had a guy come to view my car but he was 6' 8" and quite heavy set and he said he would take it if he could get another couple of inches of seat movement backwards.

 

have you had a look at the mounting points underneath, where the seat joins to the seat runners?

could you take the bolts out and drill new mounting holes?

only other option is a custom subframe or runners