I have a 225, drum brake car that I have upgraded the brakes to Wilwood discs. My question is what size ball joints would that car have from the factory? I'm looking at QA1 control arms and there are two options, 1 for small ball joints and one for disc brake cars or cars converted to factory disc brakes.

Small bolt pattern up to 1972 would have the upper control arms for the smaller ball joints I believe. When they went to the bigger bolt pattern in 1973 the spindles, calipers, and upper control arms were revised.

Thanks, that's what I figured but didn't want to assume it.

true as posted. you need to swap out your upper control arm to use the spindle and larger ball joints of the common conversion.
however, depending on the condition of your upper control arm, ball joint and bushings, our own Dr Diff may have a solution.
my one buddy wanted to convert to discs on his wife's 72 duster. this car had already been treated to new bushings, ball joints, etc. plus a set of the 73 up control arms couldn't be found [at that particular time, that matched with his tight time frame to get the car done].
the good doctor had a pair of taper adapters that were red loc-tited to the small joint pin, bringing them to the large joint pin size and taper. they were pretty cheap to boot.
i bought a pair, they were super easy to install, and have worked flawlessly for many years.
you might contact him to see if this may be a viable option for you.
just throwing this out there in case it may be able to help you out.

I bought all the front ends parts off of a 1974 A body and swap them onto my 1971 street and strip Duster I replace the wearable parts with new Moog parts back in 2002 or so, ball joints, brake pads, rubber bushings and so on
That car drove and stop very well at the track, 134.+ MPH in the 1/4 mile, and on the streets also

Thanks, I have Wilwoods already and Ill just buy the small ball joint control arms and deal with it. That was is 52 years old and hasn't had any issues with them yet.