I picked up recently an e&c qc gearbox shell. It actually seems to be ok. I've not built it yet, but it seems to be tm spec version 2 (from test fitting parts) except for the spring guide. I got it from asiaairsoft.com but Toronto Airsoft carries it too if you don't want to wait on shipping
http://www.torontoairsoft.com/EC-GEA...ox_p_2431.html
The TA version shows coming with bearing spring guide. Mine is non bearing :-/
Depending on body though, you may/may not have to pull shell to do spring change. I'm going to put mine in a g&g body where the buffer adapter screws into the lower. The qd guide just fits through that hole where the buffer adapter threads into.