the biggest problem with B body axle shafts is that every 2-3 years they make them 1/8 inch wider or more which means when you replace them you have to order custom axles if you cant find the exact year used replacement---however A and C body axle shafts stayed constant at 28 inch and 30 inch which makes life simple because you can buy them for $100-130----the A body set up makes more $ sense to the hobbyist because the housing cutdown should be about $100+ $250 for 2 new axles---if you buy 2 new custom axles from someone like moser it will be $500----yes the A body axle fits under a 70 roadrunner---done it several times---yes you have to move the spring pads--thats the something the housing narrowing person can do for you----bob