Hi guys I move my original shackles back by a quarter inch front leaf spring With spacers
My question is I have the buckets from Mopar performance I’m Looking for a measurement that you guys are using from the back of a bucket to the center of the leafspring eye

Make my own. Fit them in the car first. Transfer the stock location from the original hangers. Put the holes where I want from there. Usually moved forward a bit if they are moved at all. Along with some locations for height adjustment. Verify square and level when putting them in for final assembly.

Put the hole where it needs to be. I realize that answer might not seem to be helpful but it is the correct answer. It all depends on ride height and tire size and where you want the wheel in the fender and all of that. Mock it up, measure it 5 or 6 times then drill it. It isn't easy making sure that each side is perfectly straight and square to the chassis.

A few things to keep in mind when setting spring-eye locations:
1. Tire clearance can be pretty tight at the front of the wheel opening. Depending on tire OD, what you're building, & whether you're open to stretching the wheelhouse, spend some quality time with a tape measure.
2. I've found A -bodies vary at the front of the wheel house from car to car, and sometimes even side to side on the same car.
3. The rear spring shackles MUST point rearward at the bottom to avoid binding the springs.

If you're trying to stuff 30-31" tires into a Duster, pie-slicing the bottom of the front just forward of the flange and moving the flange forward flush with the wheelhouse can buy you that space.
When it's finished off, it looks very stock.
The same deal probably works on B & E bodies as well.
For a drag car, I've always liked moving the rear axle forward a bit if possible...

I was moving it back a 1/4inch to help with tire clearance I’m also mini tubing the car. Putting a 10inch rim on the car

Trim or bend the front edge of fenders to make more tire clearances, DON'T move the rear end back

Really!!!! Ok for weight transfer reasons!?

^^^ Yup. Pitch rotation is a lovely thing.

Moving the rear end back to make tire clearances adds more weight onto the front tires allowing the rear tires to spin easier, correct

Well SeaBee ... you could always move the gas tank further to the rear to compensate

I did the trim the fender and put the springs at the stock location with the spring relocation kit.

On my Duster project the original chassis shop screwed up the job. The boxes were built out of tin foil and the holes were drilled crooked. I had to take the car to a different shop where they used heavy duty steel boxes and they put the holes in the correct place. They had to cut the old boxes out of the car and grind everything flat and start over. That was a dirty nasty job. Good thing I didn't have to do that work! In the end it came out okay but it will never look pretty since the rework job left some scars.

AndyF do you run spacers also on your set up. I would rather shorten the wheel base or have the front hanger in the stock location but if you need room do what you must but don't over move it back.

I machine some 1/4" steel ones for my own car, which was way too heavy. I laser cut some 1/8" steel ones for a friends car, and doubler plates around the bolt holes. Worked out really well.

Personally, I don't see a point in going thicker than 1/8" if it's being welded in to the original rail. The factory sheet metal is going to be the weakest link.

I've had the front spring hangar moved into the sub frames on four different cars, first was a 1963 Plymouth Belevedere that we center the Mopar kit like the instruction said to do, the third one was on my1971pump gas Duster that I had the boxes moved all the way into the sub frames so the outer edge of the new boxes where welded against the outer frame rail to get as much additional clearances as I could on that car. The second car I ahd done was 1969 Dart and I had the inner edge of the boxes welded into the inner edge of the stock sub frames to get clearances between the stock gas tank and the leaf springs on the passenger side, I still had to dent the gas tank for additional clearances
The last one was on my 1966 Dodge Coronet and I helped a friend, a pipe line welder move those boxes all the way in also after denting the new gas tank for spring clearances on the passenger side

Some of the work we did on my son's 68 Dart 270.

And after welding the kit in I braced it with gussets.

We cut the front of the wheel well and moved it forward 2 inches. He is running 325/45 20's in the back on Foose Mags

Did you guys drill 5/8 holes or 11/16 ?

For the front spring eye bolts? Mine are 5/8".