I installed a vintage A1 pistol grip on my new Anderson lower and cannot actuate the safety selector. The spring looked like it went into the hole correctly. I then installed a new A2 grip using the same spring and detent and the safety selector works flawlessly. Am I missing something here? Any thoughts?

with the grips removed, does the same spring stick out the same distance from both grips?  same spring, detent and selector right?

Ya. Sounds like there may be some gunk in the spring hole, causing increased tension, not allowing the selector to move. It's happened to me before.

Same hole, same parts, just different outside look which doesn't effect function

The spring does protrude a small amount more when in the A1 grip.
Same parts, just different grips.

try cleaning out the hole in the grip with a drill bit. If the hole is shallow, then drill it to spec. Or just snip the spring.

+1, that extra bit is putting just enough tension to not easily manipulate the selector.

+ 1 onthe cleaning advice.
Also I have found that some selectors, and their detents benefit from a bit of counseling provided by "Clover Compound" or a mild abrasive polish to help ease the relationship between themselves.
I've had many take down pin and pivot pin detents combinations that were a little sharp or resistant to easily working with one another.
The polishing compound : grinding compound helped them work together much better.
The polishing/ grinding compound does have to be cleaned out very well, or the remaining grit will be used against unintended areas.

I've noticed that the spring hole depth can vary from grip to grip.
The shallower the hole, the more tension is placed on the selector detent and the selector will be harder to move.
On the ones that are very stiff, I usually end up clipping a coil or two from the end of the spring to make the selector easier to use.

Yes, all of my lowers have had that spring clipped at least one coil.  I would recommend that over drilling the hole deeper, if you screw up it's only a cheap, easily replaced spring.