The basic non-goto EQ6 can be modified to allow a form of guiding however it is not as flexible as the goto model because you don't have the same degree of control over the guide rate:
http://www.store.shoestringastronomy.com/eq_mod.pdf
Shoestring also sells the bits however this is just a short length of 6 wire phone cable with an RJ12 plug on the end and an RJ12-RJ12 female coupling.
http://www.store.shoestringastronomy...s/gpkit_eq.jpg