Hello I have just bought a 1971 grabber 6 cyl auto. it came with a spare parts car its a 1974 6cyl auto the 71 has a 8 inch rear with 4 lug axles ans a 3.00 ratio. the 74 has 5 lug axles and a 2.79 ratio.will the axles change over or do i have to change the center? thanks joe