Get the alignment checked.

 

Won't that much drop put the upper ball joint in a position to possibly bind? Someone will chime in.

Edit: Nice car!

 

That's a Charlie. A 2" drop would require wedges to keep the ball joint from snapping. Move that control arm pronto!

 

I did my toe with a straight edge clamped to one wheel and my 4' level clamped to the other wheel, tape measures and strings along each side.

 

I am guessing toe would increase as you loose camber.
My thinking is that the spindle will move outward at the top ball joint, which then will cause the part of the spindle below the lower ball joint will move inward, and with the arm behind the wheel, that would increase toe.
Or,
I am 100% wrong, and should not be responding.

 

After looking at the upper ball joint, which is parallel to the arm on the SPC upper control arms online, you should be fine with a 2 inch drop. The one inch "rule" is because the BJ on the oe arm is at an angle to the arm, and puts the BJ in a bind at any drop more than 1 inch. I ran my 69 with tube control arms with a two inch drop for many miles without issue. When changes are made to any suspension, one should move the suspension thru its travel motion without the spring to check for clearance.

 

Call SPC and ask them if dropping the arm 1 inch will bind the upper ball joint, otherwise I'd leave it. Shelby dropped it on the race cars between 1-3/4 and 2-1/2 inches. You'll get a decent camber curve at 2 inches, overall.....the only reason why the 1 inch drop is so popular is because of the stock ball joint impingement.

Have it realigned afterward. The change is going to affect camber, caster AND toe.

 

I did call SPC and spoke with a really nice and knowledgeable tech guy. He said it is a bit of a grey area, but recommended that I move them back to the stock location. He said that it might stress the bearings to have them that low, and there might be some binding or other weird handling issues. Said if I wanted to keep them lowered that I should check for that just to be safe, which would involve removing springs etc. Also, bump steer might be an issue which I have noticed. BTW, I did end up putting them back in the stock location today and it changed things quite a bit. Ride height seems like it is a good inch higher-kind of feels a little goofy. Also, camber is positive now, and toe seems more excessive inward.

 

The usual recommendation when you do the drop on the upper arms is to remove something like 3/16” to 1/4” to somewhat get camber back to what it was until you can get it aligned. According to the Ford shop manual with shims that 1/8” of shims on both studs will have a change of 2/3*. At least on paper. So going back to the stock holes I’m going to say in theory adding that about should get your camber back roughly until you get it aligned. As @Bart said, everything is going to change. Bart knows his stuff but I’m wondering if caster will change only because to change caster you have to alter the shim pack thickness front to back.

BTW, those are the exact same settings I’m using, 4* caster and 1.125* neg camber and 1/16” toe in. You can also just leave it as is if you get use to the ride height.

 

but I’m wondering if caster will change only because to change caster you have to alter the shim pack thickness front to back.

Caster will change because the "drop" on '65-66 cars involves moving the upper arm back 1/8 inch. Returning it to the original holes will move it forward and decrease caster.