I assure you there was never a 2.75 TH400 gearset. You can veryify my info from an ATSG manual, GM Service manual, HP Books by Ron Sessions, etc. it just did not happen.
I'm sure some of the other builders can verify this also.
I just sold a built up 200-4R. You're right, they aren't cheap. I started figuring the total parts it takes to build one, it adds up.
Billet forward drum- $420
Rebuild parts- ~$200
Valve body kit- $75
oversize boost valves $30
If you use the desirable valve bodies or cores, add $250-600 to the cost.
I ran the 200-4R with 3.73's and it worked well, I would probably use a 4.10 if using it again.