I just finnished putting a 75 camero under my 51 AD. not too difficult, lots of measureing and head scratching, chassis must be on jacks and perfectly level, front to back and side to side find center line of front axle, measure back 20 inches or so, on my truck it was just ahead of the foreward cab mount, do the same with the sub frame,leave 4'' for overlap than cut both . pick up sub frame with a cherry picker and move it into place, lots of trying and fitting to do. place a place a degree level on one of the top A arms 6deg. is a good place to start, tack weld and check for looks check your scrub line from bottom of front wheel to bottom of back wheel ( wheel not tire)
amount of rake is determined by degree of caster on a frame i try to stay high, you can always torch a spring coil. good luck