904 Rebuild

Im no transmission guy by any means.
I took my 71 Swinger in to have the 904 auto rebuilt by a reputable shop.
The guy called me today and said the trans has never been serviced or opened, that he can tell, in the 40 years of its existence.
He suggested it be totally rebuilt with all new bushing, plates, bearings and etc. and I agreed
Im having him go ahead with the TF-2 shift kit while he is already in it.

Total cost with labor out the door is $1,400. What have others seen with a rebuild like this?