Thanks Jerry, There's some great info in those pictures.
I figure I'm going to make the chassis a bit wider than the original dragsters. I've got to fit a powerglide in there and get my feet down each side of it too. From what I've read most FEDs were in the 19-20" seat width. That's just to tight for me as I'm a bit wider across the shoulders and getting wider round the middle. If I make it 23-24" inches wide I should have a more comfortable time in there. It will also free up some space to get my legs over the diff.
I'll probably have to use a more upright seating position like the moder FEDs apearing these days.
I'm having my belly button relocated to take care of the offset issue.
Cheers