Welcome to Stangnet . The 67 -70 has a better suspension than the 65-66 but you can upgrade it .A 65-66 should have some chassis strengthening and a 67 needs one torque box added .The 68 -70 has the strongest chassis out of the box but you can make upgrades to them as well .67 -70 tend to be a little more expensive to build than a 65 or 66 but any one you chose will be a fun project .