Here's one of my '74s:
 
 

 
I can't imagine ever parting with it.

I own a 83 Distillate and a 71 Jazz in mint condition. No comparison  the Alembic has it over the Jazz. My Lakland Joe Osborn sounds better than the Jazz, My Jazz is unique and probably one of the better Jazz basses that Fender made considering the mid 70's models were a joke with mismatched parts etc, With a good amp set up you can really hear the differences between the basses but that's for  another discussion

So my question is could a person trade the Alembic for the J-bass, sell the J-bass, and buy a nicer Alembic?
 

I would will never part with my Distillate!*
It is shameful enough that I sold a beautiful zebrawood Exploiter.  
 
* when I pass my son will inherit it

So my question is could a person trade the Alembic for the J-bass, sell the J-bass, and buy a nicer Alembic?  
 
It's a pretty even swap $$ wise.  
The Jazz is more valuable if it's a custom color or in mint (unplayed) condition;  
less valuable if it has any non original parts.