I would look good an hard at the rotor.  Not sure where they came from, but I've seen crappy Chinese made ones have the entire center separate from the disc due to bad metallurgy. 

I did the one in Shelby drop last winner I put new moog  upper and lower control arms which had new upper and lower ball joints I installed new strut rod bushings and had everything realigned

Did some checking today if I hit the brakes hard and come to a complete stop when I release I hear the noise so I had someone else drive the car to a stop and when I looked under the car when they release the break I could actually see the caliper snapped back about a quarter inch it did this repeatedly on panic stop I do have a rod and custom front  just brake conversion kit that has a bracket that excepts a GM caliper I’m going to contact them tomorrow to see if there’s any problem on their end

Thanks

Rufus68 wrote:

On my '68, if the strut rod end is not tightened properly, it can move by compressing the bushings during a hard stop.  Does this apply to the '65s as well?

 
Yes, the bushings compress quite a bit on a hard stop.

As for calipers moving 1/4”.   Yes, something is amiss.  Gotta love putting GM parts on a Ford!