After a couple trips to the fastener store I finally had a chance to mock up my disc brake setup.
First, the 2.75" bolt length listed in the Ebay ad was a bit too long.
I'm not sure if most of the spindles on the aftermarket disc brake conversion kits are the same thickness but a 2.50" length bolt worked much better for me.
After installing the bolts and putting everything together the bolt heads did not rub on the back of the rotor but were VERY close.
I'm not sure if the rotors move/flex any during braking or hard cornering but after about 1/2 hour with the bench grinder I was able to remove just a little of the material from the 4 bolt heads to give me the clearance I was happy with.
Total cost for 4 grade 8 bolts and lock nuts was $5.47.
Now if someone can tell me how the he** to get the dust boots installed on the Moog ball joints