This is how a 1969 chevelle floor pan is tied into the rockers, which is probably all together different then what you have, but its how they keep the strength of it because a lot of them are put in with only plug welds.
http://www.1969supersport.com/floorpn8.html
Heres some sheet metal thicknesses if it will help.
http://www.1969supersport.com/smthoughts.html
Rob
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