Hi Ken,
I have just bought an SLX kit with 3 HFT lenses (50, 80, 250) as a backup to my year-old 6003 outfit. I have not tried swapping lenses yet (body is in for CLA), however, my reading and observations confirm the compatibility of the older lenses with the newer bodies was planned, and is as described above, but with these caveats: 1) while there are enough contacts, some of the metering capabilities (especially the 6008-specific metering tricks) cannot be performed with the older lenses, but since you don't have a meter, foggeddaboudit. 2) the older HFT lenses will audibly stop down a moment before shutter release, and give anyone not familiar with that momentary heart stoppage (or perhaps cause a subject/model to blink). 3) the older lenses are mostly Bay VI, whereas many of the newer versions are screw-in filter mounts. 4) the grips are different, and so are the attachable focus handles (older are leather-like and smooth; newer are rubber with nubs or ridges for gripping. And finally, 5) the costs of the older lenses have come down. This is why I decided to go for the SLX set, and sell my Pentacon Six TL kit. While the leaf shutter HFT lenses are still more expensive than the Carl Zeiss Jena/East German lenses for the Pent 6, they are virtually interchangeable with my main 6003 camera, and thus I eliminate the entire seperate bag of lenses (not to mention the dramatic difference in sophistication between the Pent 6 and SLX bodies/meters etc.)
I will note that the motors were upgraded in these lenses, I believe when the 6008 series came out (maybe earlier 6000) and the new motors are faster and stronger (and don't have that staged release factor above). I also believe they were part of the reason for upgrading the main fuses in the battery from .8 & to 1 and then to 1.2&s. Of course, the PQS lenses fire up to 1/1000, which I think your camera is capable of.
Anyway, you may use the older lenses and save some money, but consider the limitations I've mentioned when selecting them over a newer model. I know you'll enjoy the 6001, but bear in mind that you are missing what is arguably the BEST metering system on the market. It is truly astounding, so if you can find an upgrade to 6003 of 6008, you ought to consider that among your other (lens, prism finder (also compatible), etc) priorities.
Best wishes,
Ray Hull