Do you mean Front Frame rails? ( not subframe connectors, I think the two terms are interchanged alot , and causes alot of confusion , at least for me.) Pete has good info for subframe connectors (link given above), that is what I used to build mine , as for front frame rails , I have a post http://forums.hybridz.org/showthread.php?t=94710
where I made mine, and the drawings I made are available in the post as a PDF file.
This is for a 78 280z, the 240z's may be different.