If your car is stock powered and stock body, a well maintained set of stock calipers and decent pads will lock up any tires you can make fit under the stock narrow fenders.
This question comes up several times a year, the group here can get a little testy when hearing it again, because most have been there, done that, and have written a bunch on this site on their findings. I may be jumping the gun on your original question, but I know “big brakes” and “more horsepower” sound super sexy, but it’s expensive and time consuming to get there.
Assuming you’re not made of $$$, there are much better places to start spending your hard earned cash on these cars.
I know the pedal feel is not at all awe inspiring, but you’ve got 4 wheel disks on a 70’s era car that weighs less than 2500 lbs wet. Let that sink in and go from there. Get a good set of stainless brake lines (dot approved), some good pads, and some good fluid (ate typ 200). Learn how to bleed the brake system (FULLY), and properly adjust the rear calipers. You should be able to lock the brakes easily.
If you still don’t like the feel (pedal too soft), move replace the master cylinder with a 19 mm MC. That will firm up the pedal.
Learn how to “heel toe” and watch some stock 914s carve up the twisties or compete in autocross.
Read everything you can from this site, there is not a better group of gearheads, who are willing to guide anyone who is willing to listen.