Once you start talking bigger valves another whole can of worms there. If they do not accurately bore the throats below valve bigger to suit the new valve and the necessary handwork that follows then the new bigger valve often LOWERS flow as it then blocks the flow hole more from the bigger size. You'll definitely be in MUCH higher cost doing that work. The job requires some extra tooling and not nearly any shop will be able to do it, but that doesn't stop them from telling you they can.
The throat size and valve size are picked to be complementary to each other. Bigger valves from other engines often mess up the geometry due to length too, and not just anyone again will have the ability to shorten the valve if needed.
We found back in the days of the family shop that a lot of 'bigger valve heads' we ran across were pretty much junk, including some pretty high dollar shops. Lots of ways to get it wrong and only a few do it right. Buyer beware is the word there.
Just sayin' and no impinging of any name that is mentioned in this thread is intended.