New Guy with questions

[JackB]

Hi all been lurking here for a while and finally bought a 71 Blazer and I was hoping you could help me out with a couple of questions I have. I picked the Blazer up at an auction so I know very little about its history. What I do know is that it was last titled in Oregon and I'm in CA so job one is going to be getting it registered here. Which leads to question one. The vin/partial vin on the SPID, the VIN tag, the blue federal door tag and the frame all match (Pics attached) but I'm concerned that the rivets attaching the vin plate appear odd (Round not rosette). It looks to me like the tag was cleaned up/polished as part of a recent paint job but it really doesnt appear to have been removed. There is still some dirt around the rivet areas which seems to me would have been removed if it was cleaned off the truck. I found another picture of a original tag on this site that looks as though it has never been off and the rivets are round. Are there known instances of tags being attached with non rosette rivets? Can the rivets be rounded off somehow with heavy cleaning? I'm concerned that I may run into problems with the CA DMV because of this so I'm looking to learn as much as I can prior to going.
Second question..Is the partial vin stamped on the engine anywhere? Its not on the pad for sure. Assembly stamp is V0607TBD. Appears to be original engine as the assembly date of the truck is 6/71 does this sound correct?
Thanks in advance for your help. More questions to follow I'm sure