Which Nakamichi to choose?

If you're thinking about archiving precious records, don't think twice. Get a Nak. The medium is viable, the sound good, the build excellent.

What's the consensus these days on whether or not to use Dolby when recording?  Proper bias is of course very important, but would you archive vinyl using Dolby?

Thanks, @terry9 . I still have my notes on the various Nak models when I was looking to buy.
I worked in studios and am very familiar with how quiet R-R and cassette can be. I'd like to try transferring CD's to a high-end cassette deck; I know analogue tape bestows a nice sonic quality to the recording.

@jond , I agree with you; I tried it and decided against using it. I think everybody back in the day tried it and came to the same conclusion.
  I still have tapes that I recorded with "Dolby On."

@terry9 , the CR-7a must be like "studio quality," (I realise we're talking cassettes).

Would Dolby B on a stock CR-7 effectively reduce noise w/o limiting sonics?

Thanks for that info, @tls49 . I still love analogue tape and have considered a used Nak to archive vinyl.

Was Dolby C of any use on the Naks?

Great info, @cleeds . And the term archive is a misnomer. My plan was to make high quality copies of albums that can be listened to without the time and effort of playing vinyl.
  I agree that R-R is an amazing format even today, but requires money, time, and a relationship with a good tech for use in a home system. I enjoy the setup and recording process. Then comes the satisfaction of sitting back and listening to some outstanding music.   
   For me, there's no other format that sounds so pure and organic.