Are there problem areas on the 67-68 Barracudas

common areas of rust on the cars i've had and recently purchased include:

bottom of both front fenders.
under the hood on top of fenders back close to the hood support hinges
rust around the rear glass on fastbacks
rust on the "torque boxes" on under-body frame rails
rust in the trunk spare tire floor pan
rust on front driver/passenger floor pans and rust on rear passenger floor pans
rust on lower rocker panels below doors
rust on rear lower quarter panels in front of and behind rear wheels

other things to check are:

whether all gages work
wipers work
fan motor works
turn signals work
radio works
interior light works when doors open
brake lights work
head lights work
back-up lights work
brakes work
emergency brake works
high/low headlight switch (on drivers floor) works
all windows crank up and down fully
drivers/passenger door locks work
trunk key opens trunk
ignition switch works
check play in steering
does the heater control slide bars slide back and forth
put turn signal on, turn steering wheel to see if the automatic reset kicks the turn signal off

check engine oil for water bubbles
check auto trans fluid and check for a "burnt" smell
check radiator for leaks
see if windshield washer fluid plastic reservoir is present and not broken
look at firewall to check to see if there are a bunch of wires that "don't look factory" - look under dash for same thing
on 4 speeds, check shifter, drive if you can to see if trans has all 4 gears and revers - or slips out of any gear
check clutch for slippage, burning smell, "chatter" upon engagement, clutch pedal not coming all the way up from floor
check auto trans if drivable for forward/reverse shifting through three gears

the above is not an exhaustive list of things to check on a car you're looking at but is a very good start. remember, these are old cars, a lot of the things on my list will need fixing/replacing. but if you make a list of all the stuff that needs repairing, you'll get a good idea how much time you're going to spend on a car.