I think your thought process is off.
Unless you strongly suspect you have 30 gal of rotten bacon grease in one and a petrified sht mountain in the other, both of which can’t be removed, I feel it’s still a venting issue.
I mean, tanks all stink after a few days or week of use, so what makes one think that a new tank getting the same use won’t just stink after a while.
I could be totally off base and who knows the use condition and care of YOUR tanks besides you. No one. Just seems odd to me.
Idk what it will cost but won’t be cheap when you roll a 40’ pusher in for “elective” surgery.