Sheet Metal
 

I asked a question earlier about drilling into chromoly tube,putting in a nutsert to install my fuel line and I got some good replies. My next question is if I can't really drill into the tube ,how will I fasten the sheet metal to the floor then if the chassis is all round tube.
Any help would be appreciated.

You can use DZuse fasterners. They have a tab that you would weld to the bars. Also check racing supply places and look at there body mounting stuff. Another option is weld on tabs and the you use pop rivets to hold the pannels on.