70 k5 body with 72 k5 frame problem

[J*ROD KUSTOMS]

i finally found me a k5 and started the resto. the k5 is a 1970 chevy cst 4x4. when i bought the blazer the front end was smashed and frame was bent. so i bought a 1972 4x4 frame and converted it to 2wd. now that im mocking up the body to frame i noticing some diferences. the major one is the body will not sit because of the rear frame and brace of body, my 70 frame looked cut in the rear and this 72 had horns to mount the bumper, were the 72 body and 70 body different or frame?