I'm building a 69 Camaro with a LS1 and 4L60E trans. I have a turbo400 Crossmember on hand. What kind of mods do I have to do to make this crossmember work?

#1... Put the mounting plate on center! It is offset approx. 1". Do you have the old Th-350 crossmember also ? You may want to see if you can just slide it back on the subframe and drill new holes.