I knew this might be an issue as these aftermarket grade top spindle bolts I picked up has a taller head than the original.... and a MUCH taller head than the thin aftermarket ones with no head markings.

Not the best pics... but you can see how close they are together, and I have the spindle castle nut hand snug right now. Safer to just reuse the original (L8 marked) bolt instead?

 

I wouldn't think it would cause a problem, you have the tang in place to keep it from backing out. The only way I can see them coming in contact is if the wheel bearing goes bad. Are the current bolts grade 8?

 

That's way too close for comfort, that may even get closer when the brakes are working from heat expansion and when you hit the brakes the caliper will also want to pull or push the rotor in towards that bolt. They wouldn't of originally used the thinner head bolt for no reason.
Why not use the original bolt?

 

Don't really trust 40yr old bolts, especially when they need to be ~95ft lbs. Also looking ahead to another 40 yrs I guess. Below is my original (left), and the really thin head (with no grade markings) repro bolt (right). So I have 3 diff kinds at present... the one installed now (which is thicker than the original by 2-3mm or so), then the two pictured below.

 

I reused my original with no hesitation at all. If you had not taken the brakes apart they would still be in use correct?