Body tub swap - DMV info

[Peter Ficklin <pficklin@qnis.net>]

Listers,
  Does anybody have any experience with the DMV, CA specifically,
relating to a car getting a body tub swap?  My son's Spit (FD 30015 L)
has got some rust in the sills & floorpan, and I've got a pretty
rust-free tub (FD 2295 L) and we'd like to swap them.  Both tubs have
comm plates, and I'm wondering what hoops I've got to jump through to
get the car properly re-registered with the FD 2295 L plate on it.  Any
advice greatly appreciated.  TIA

Peter Ficklin
'63 & '68 Spits - maybe a '67 now!