At the local co-op I picked up a VGT Luxe Derailer or cheap and found this GT cage in the bin with the rest of the derailleurs. This cage looked exactly like the cage on a cyclone MKII GT, so is it same to assume I could swap this cage onto a standard cyclone and it will become a long cage version?

I've never tried it with a MkII, but have done it with an early Cyclone (if my memory isn't playing tricks on me). steelbikeguy will know for sure.

dang it, now I have to go and look up the difference between the 1st generation and the Mk II.

To be honest, I wasn't sure I could tell you what the difference is, but a quick perusal of my various teardown photos produced a good shot of a Mk II cage:



the key (only?) difference is that the Mk II has a hex hole for the lower pivot shaft, while the 1st generation has the threaded round hole as shown in the OP's photo.

It is possible to put a 1st gen GT cage on a 1st gen short cage Cyclone body, which I've done. The short-cage Cyclones come up on ebay for a bit less money than the GT's, possibly because low gears are becoming more popular among the vintage crowd. Having a spare GT cage such as this one would be handy for such a conversion.

Steve in Peoria

At least on the first generation GT, you'll need the long-cage bolt.

The short-cage version has the cage pivot bolt screw into the cage, whereas on the GT version the cage pivot bolt also does double-duty as the axle for the jockey pulley.

Thanks for that extra, essential detail! It completely slipped my mind.

Some shots of the short cage derailleur and pivot bolt....






and the GT version....





Steve in Peoria