I've looked around a bit and can't find the thread that discusses this...

Will a 12 bolt from a 68-72 bolt right into a 66? I seem to recall there was a 1" difference in overall width, but everything else was the same. I'm wondering if the spring buckets will line up and, well, everthing else?

It Will Bolt In If You Use The '66 Control Arms. Spring Pockets The Same,but I Think It's Actually 1.5" Wider.

I've looked around a bit and can't find the thread that discusses this...

Will a 12 bolt from a 68-72 bolt right into a 66? I seem to recall there was a 1" difference in overall width, but everything else was the same. I'm wondering if the spring buckets will line up and, well, everthing else?

Everything lines up. The issue will be the spring eyelets for the later 12 bolt are going to be different. The older rears used a flat spring perch and a plate / clamp that held the spring to the perch. The newer rears have a bump (for want of a correct term) that the spring sits over. The later rears are therefore easier to install on the assy line. All that was required was to set the spring over that bump, no time and labor had to be expended installing the clamp and the bolt for the clamp. Oh yeah the 10 seconds tightning the bolts was also eliminated.

I have read that you have to use the arms from the CAR the rear is going IN NOT the arms from the rear the car came out of. This is more important on the upper arms. Apparently the lower arms are interchangeable between cars and rear regardless of the year of the rear or year of the car.

On the springs. I cannot remember the swapping rules on those. It can be done W/O changing the lower spring pearches but someone else is going to have to fill you in on the particulars of that. Old rear have to use the clamps but I think the new springs will work on the old rears...but you must have the clamps. Said more clearly whatever spring you use on the older rear you MUST use the clamp / plate. The lod springs might work with the "bump" on the newer rear lower mounting perch but I dont know.

Springs and arms won't be an issue as I'll be getting new for both. I guess the main thing to remember there would be to get the arms for a 66 and the springs for the new(er) rear?

Springs and arms won't be an issue as I'll be getting new for both. I guess the main thing to remember there would be to get the arms for a 66 and the springs for the new(er) rear?

Yes

I ended up buying a 1966 12-bolt, but will have to weld the brackets back on to the tubes as it had been converted for a leaf-spring truck. This should be fun.

There is a 66 12 bolt in classifieds for 350.Was yesterday anyways.Open but still a good buy for housing.

Springs and arms won't be an issue as I'll be getting new for both. I guess the main thing to remember there would be to get the arms for a 66 and the springs for the new(er) rear?

No, get the springs for a '66 also.

64-66 had a single-pigtail spring with a full coil on top, and the pigtail on bottom.

67 and later they changed the spring pocket on the frame to use a double-pigtail spring. 64-66 springs will work in a later car, but the later springs will NOT work in an earlier car.

The spring perch on the axle changed designs, but the pigtail on the spring remained the same and any year spring will fit either axle perch.

Lower arms are the same from 64-72, but the uppers were longer on 64-67 cars than 68-72.

Does anyone know where I can get a refference for measurement points that specifically show the width differences between a 65-67 and a 68-72 12 bolt?