Jeff, I just finished registering my 51 suburban with 51 YOM plates. They are regular plates because suburbans were meant to carry passengers.
(no tag needed because it's a 51)Panel's where primarly used as work trucks.
So in your case,You might be looking for 51 YOM commercial plates with the added 52 tags
I know for a fact that they will not let you run the 56 or 63 plates on a 52.
As far as turning in your 63 plates, since they will be clear at that point, Tell DMV that you would like to pay the $20 or $25 dollar fee to maintain them clear. This way you could keep them and use on a 63 and above vehicle or sell them. (or maybe mail them to me

)
Not sure on this, but it's worth a try.
I like the idea of ordering the plates with the same numbers, but keep in mind that now they will be personal plates and you will have to pay additional registration fee's every year.
With all this in mind, I found that if I educated myself a bit before entering the DMV it will work out fine. I was teaching them new things. :confused:
Hope I was of some help and not confused you.
Good luck!
Javier