Hi Jay. For your FYI. A small block V-8 will fit into your 66 just fine without changing any front end components but, your going to want to anyway simply because the stock equipment from the 6 banger is lighter and youl want the heavier duty V-8 suspention parts to go with that supped up small block your going to build later. also consider changing out the rear axle unit as a whole. You get heavier duty breaks and larger eveything when going with a rearend from a V-8. Pay close attention to the spring pads and overall width on the rear end. Early V-8 Falcons, Fairlane and Commets will work by simply cutting and re-welding the pads where you need them. Have fun...
