GBIC connector

The 3550 use SC style GBIC's, the 3560's use LC style GBIC's so you will need to use a LCxSC fiber patch cable if they are in close proximity to each other. Very common item. If they are in different closets connected by infrastructure fiber then that will depend on what is in the cans, either SC or ST.

Goto

I am sure that the OP would find this less confusing if the correct terminology was used.

The LC adapters are SFP.

I am aware that quite a lot of people use the term GBIC to mean any concievble design of modular Network interface adapter however if you want an SFP then you are not going to find the right stuff by searching for GBIC on the Cisco web site.

/rant

Sort of true. SFP stands for Small Form-factor Pluggable. Some references say this is a Small Form-factor Pluggable GBIC, so it may not be entirely false to refer to an SFP as a kind of GBIC, but I agree it's certainly confusing. There's also some confusion about whether a mini-GBIC and an SFP are the same thing, but I'll leave that for another day.

Sam