Is this for your wagon with BBC? The TA discs will not give you a noticeable improvement over a good rear drum setup. The only possible slight benefit would be if you were going to use the car for auto X or mild road track duties. 2nd gen TA guys have been doing the swap for years, I considered it for my bird at one time but ended up using race compound shoes for road track duties in finned drums.
That said, if you want rear discs for looks, a "Right Stuff" rear disc conversion can be bought for under $500.00 and under $400.00 without park brake that fits in most 15" wheels.