Thanks guys.
I'm startig to lean towards 1.2mm SS
18 Guage is about 1.2mm and it will be internally braced with baffles so I reckon it should be stong enough.
I am a little concerned about welding material that thin. I'm buying a whole sheet of SS so I'll practice a heap on some offcuts till I get it down pat.
Jerry, I'll have to drop you a PM to quiz you on your welded setup. I'm still learning my way round this new AC/DC machine. My old straight DC unit was a lot simpler. I haven't got into using the pulse settings yet.
I'm still finding parts and pieces for the Dragster. There's Australia's biggest swap meet on this weekend so I'm going there cash in hand.
Everyone has pretty much talked me out of using a Quick change diff. Several stories of splitting centers and broken side bells has cured me of any desire to sit with my legs either side of one. I've been looking at a really nice Aussie made 9" housing.
http://www.crdengineering.com.au/products.asp
Cheers