Actually the TF39 is the mother of all the CF6 series of engines. The TF39 shares its HPC core with the first model CF6-6 used on the DC-10-10. The main differences between the engines were that the TF39 has a 100inch 1-1/2 stage fan and a 6 stage LPC and the CF6-6 has a 86.4inch single stage fan and a 5 stage LPC. It is interesting that they made the same amount of thrust at 41,000lbt. You are correct about the differences in the BPR's. While the TF39 has an 8:1 BPR the CF6-6 started life with a BPR of 6:1.
There are of course further developments of the CF6 series of engines and the subsequent models have significant changes from the TF39 parentage. The CF6-50 was the next major step in the line. The main changes being a reduction of HPC stages from 16 to fourteen, a reduction in LPC stages from 5 to 4, and the addition of 2 more stages on the LPC aft of the fan. The fan included repitched blades and the combustor was redesigned as well. All of these changes added up to an engine with a 4.4:1 BPR higher PR's and lots more thrust taking the CF6-6's 41,000 to over 50,000 on the CF6-50C2.
As the CF6 engine family has been developed it moved even further from its TF39 roots. The next step in the development was the CF6-80A with a basically unchanged fan, and another combustor redesign. There was also another significant change in the design with the engine having the accessories mounted on the core instead of the fan case. This was something interesting because the TF39 used on the C5 aircraft had the accessories on the core from the start while all of the CF6 models up to the -80A had theirs mounted on the fan case. You can find the CF6-80A's on airbus 310's and early 767 models. It is almost indistinguishable from the next-to-latest version of the CF6; the -80C2. The CF6-80C2 improves on the -80A with a 93inch fan, vs 86.4 for the -80A, and an additonal LPC stage behind the fan, bringing the total to 4, a fifth stage on the LPT, higher turbine temperatures and new materials to bring thrust to over 61,000lbt with a BPR of 5.4:1 for 767's, 747's md-11's, and the newest Airbus A310/A300's.
The latest growth stage, the -80E1 has given the venerable basic CF6-80C2 a 96.13inch fan vs 93in, higher temperatures, some internal structure and aerodynaminc changes to produce up to 71,500lbt with a BPR of 5.8:1 for the A330.
It is quite interesting that the decendants of the TF39 have all maintained the same basic core design, even down to some of the dimensions and geometry of the HPC. Its hard to belive when your looking at a brilliant modern-day CF6-80E that it still posseses basic design elements that first ran 34 years ago.
I hope that my little rant gives you some useful information.