Since your car is older than 1976 model year, you don't need an emission test to register it.  Lucky for you 'cuz emission label or not, there's no way you could have registered it with a V-8 under the hood if it was a '76 or newer! 
When you get the DMV I'd keep my mouth shut about the engine.

As far as I know the label is insignificant for the Calif. DMV to register the car.  While it goes back nearly 10 years I had similar worries.  I actually found the label on the internet and printed it to white contact paper.  Then I placed it under the hood (smudged with dirt and grease to look old).

When I went to the DMV the woman looked at the VIN plate through the windshield - and the one on the drivers door jamb.  She never lifted the hood even though the VIN was stamped on the firewall.

This was on a '73 Datsun 510. Talk about hard to find parts for!!! The car was gutted for autocross including the removal of the dash.  Thankfully the guy I got it from had the dash VIN plate on the key chain.  That said, the DMV insisted the VIN be on the dash and it took me 4 years to find one in even marginal condition.

Tom