hi
i have a1968 chevelle. and would like to know if the front disc brakes (control arms, spindle, rotors, calipers )from a 1978 pontiac boneville will fit my chevelle . i own the pontiac and the front end was rebuilt 8-1-05 and now the car is not running and is going to be parted out. and i know no one is going to give me the amount of money i spend on the front end so i might as well try to make some good use out of it. thank alot for any help.

Bonnevilles are B-body, which have the "tall spindle" which is a common swap.
Here are the ins & outs of that swap. :)

“Tall” Spindles: This topic always creates controversy. Some guys love them, and others equate them to the anti-christ. There are positives and negatives, but overall it’s an affordable mild performance upgrade, with parts that are easy to find. The praises of this spindle come from the option of using 12” rotors, and it’s height, which changes the geometry favorably by increasing negative camber gains in compression, giving the tires more bite to the pavement. The stock Chevelle spindles are 2” shorter, and actually create positive camber in compression, causing only the outer edge of the tire bite the pavement. The negative effects from this spindle are spawned entirely from the steering arm location, which creates bump-steer issues much worse than the stock spindles. The length of the steering arm will also make your turning radius wider, and slow your turning ratio. These spindles will lower your car about 3/4” from stock, and widen your track-width, so larger backspacing wheels may be needed for fender clearance. Aftermarket upper control arms, or offset cross-shafts will be necessary for a proper alignment. The offset shafts are much cheaper, but some people have clearance issues with them, especially on big-block ‘64-67 Chevelles with headers.

The choices for donors of “tall” spindles is determined by what size brakes you want, 11” or 12”. The ‘73-77 Chevelles have a tall spindle that uses an 11” brake with a 4-3/4” bolt circle. ‘77-’90 Caprice (civilian) sedans also had 11” rotors and 4-3/4” bolt circle, however the ‘77-90 Caprice police-package cars and station wagons, and all ‘91-96 caprices used 12” rotors and a 5” bolt circle. To adapt to a 4-3/4” bolt-circle, you can use the 1LE police package ‘89 Camaro rotors. The ‘77 model year spindles will not work because the outer bearing was smaller, and will not fit with the 1LE rotors, and the late-95 and all 96 spindles have a 5/8” lower ball-joint rather than a 9/16”, so for this swap it is recommended that you use ‘78-94 Caprice 12” brake spindles. If you are doing this swap, it’s worth the extra money to upgrade to the 12” rotors because their larger size allows them to absorb more heat, the increased surface area helps to dissipate the heat more quickly, and the extra leverage allows more stopping power with less effort. The 12” B-body brakes are the largest brakes that will fit inside a 15” wheel. To adapt the B-body spindles, you use the B-body calipers, bearings, and ball-joints, G-body tie-rod ends, and the Camaro 1LE rotors. The lower ball joints need to be machined to fit the chevelle arms. The wheel studs are metric, so metric lug-nuts, or changing the studs will be necessary.

thanks a lot for the help . i will be looking for the offset cross-shafts.if you can tell me wher to find then it would be a great help. thank you very much.

Check your local NAPA type parts store. If they don't have them, they can get them for you.

You need the offset to achieve more negative camber, which means they need to be installed backwards from their intended use so they offset the control-arms inward, not outward.

thanks alot for all of your help i will be making a trip to napa. thanks

Check your local NAPA type parts store. If they don't have them, they can get them for you.

You need the offset to achieve more negative camber, which means they need to be installed backwards from their intended use so they offset the control-arms inward, not outward.
I'm guessing thats why the shop that aligned my car after they installed the offset cross shafts had to use so darn many shims. They installed the cross shafts the way they were to be installed per the directions (I have the "taller Spindles).
I think I'll get them to re-do it. $$$