I've also done it. I find the sticker thing to be weird. I have a few sets of original plates w/ 40 years of stickers stacked up but to use them for YOM DMW insists that the YOM sticker is visible, i.e. 1972. And you can't stick it on top -- it has to be the first and only sticker. There is no way to peel off the newer years so you're forced remove genuine history to buy a fake aftermarket sticker -- which then all have the same serial number. A nice market for the sticker sellers. If you actually had a car w/ original plates it would have the sticker stack and current year sticker visible. With YOM you get a little metal tab to stick current stickers on, which you're supposed to bolt to the plate. Heaven forbid if you cover up the repop YOM sticker. The idea is that you would remove the tab at your car show. It's dumb but you have to play the game.
Keep in mind, if you want to do it right you need to get the proper letters. California recalled all the 56 (yellow w/ black) plates in 1963 and replaced them with black and yellows. This was stupid and used up about half the alphabet instantly. Thus, a 1964 car would have a plate in the M-N-O rage, 67 was S-T, 68 U-W, 69 W-Z and then they ran out and introduced the blue/yellow with the number and letter positions swapped (numbers first). So 1970 started in the A-B range, etc. It would look wrong to have a 123 SOS plate on a 72 as they didn't get into the Ss until 78 or so. In 1980 they introduced the 7 digit (1 number, 3 letters, 3 numbers) system and the blue on white plates.
Personalized plates were introduced as an option in 1972. In 2012 CA DMV offered the ability to get black and yellow (63-69) plates for current personalized plate numbers. At the time they also advertised blue and yellow (70-80) plates. I applied for a blue and yellow set but there wasn't enough demand. Instead of refusing the order, they sent me black and yellow plates, which are incorrect for my 72 so I had them repainted in blue and yellow. Picky people (that's you
@HB Chris) can tell the difference in spacing/font/metal (alum vs steel) but personalized plates were available in blue and yellow and I think the repainted new plates look good and period correct-enough. And I can apply current stickers w/out any dumb external tabs.
In 2015 California introduced the Legacy plate option of getting sequential 6 character (or personalized) plates in black and yellow. Personally, I think YOM and Legacy programs have diluted the beauty of original black and yellow plates. It used to be special to see an old car w/ an original plate. Now half the Teslas in town have black and yellows. It has actually made the blue and yellows more rare and eye catching.
And yes, front plates are always required in CA. You can't register YOM plates w/out bringing in a readable pair.