You might find some helpful info here;
http://forums.maxperformanceinc.com/...d.php?t=608643
The 75 -81 subframes are a bit different,as are the mounts,but same concept/location.
I'm not looking at a 70-74 subframe right now,but can you get access to mount plate bolts through the mounting holes for the lower control arms? (long extension/flex-socket?)