31 chevy registration

i just bought a 31 chevy sedan, i have the body tag but no serial number. how do i go about getting one or what else can i use, i dont have the original engine, i'm using the engine out of a 50 olds 88.

 

The serial # plate was located under the front pass seat area That is where the serial # was stamped, the cowl tag was only the model # unless it was a Canadian built car then the serial # was stamped on the firewall tag...so I've been told anyway.I guess you will have to go see the state of CA to get it fixed or maybe find the doc's on line

 

yeah.. there isnt a floor. so i dunno where to start really