The bases of the Progression 602FC and the Progression ST II look the same…but oh how deceiving looks can be. Under the Red FRP cover there are few significant differences between the two. The main differences are in the cast aluminum frame underneath the red cover and the turntable pin shafts that connect the suspension systems to the base.
The 602FC has a Turntable Pin that slides into a Bushing in the cast aluminum base. It is an inch or so in diameter. The ST II has a Turntable Pin that is much more complex which includes two sets of bearings that fit into a support tube that is around two inches in diameter. That assembly then fits into a larger sleeve that supports the Winder Track Bar, which in turn slides over another sleeve connected to the aluminum base.
Because of the larger diameter required to support all of the “stuff” for the ST II the base on the 602FC base would require a lot of machining and fabricating to adapt it. You would also need to be able to lock the shafts into position so that the Winder Bar stays parallel with the length of the base. If you, or a really good buddy, can weld it may be possible to make a flat flange with a tube welded to it and bolt that directly to the top of the base. It won’t be pretty at all, but “might” work.