Yes, but read the ops post
He is NOT going to deep cycle the batteries.
He is only using them to start. He's taking a camping light. No refrigeration.
Where, tell me is there deep cycle in his elec usage?
Read his post.
Actually, I did reread after this post, YOU need to reread the post, This sentence does stand out as not only needing to start the motor, but run on occasion the running and house lights, along with CB radio!
"My needs are modest. It primarily needs to start my Farymann A30, single cylinder, 10HP diesel. I have the usual running lights and house lights and VHF radio."
Reality is, he "could" get away with a single dual purpose battery, or two dual or Deepcycle batteries, or a single ea starting and house battery! The best option no matter how one slices it, is two batteries, not a single one. If the house, running lights, CB etc drain the batter too low, he will not start his engine! Hence why most of us will recommend 2 separate use batteries.
Now if one wants to argue about the size of ea, I'm not going there! as that has too many variables that come into play! Some would say his current 2 8D bats are too little! others a single size 24 75ahr battery is plenty for a house bank!