MGA 1500 has four wheel drum brakes, and they work quite well. MGA 1600 has front disc brakes, and they work quite well. MGA Twin Cam (and "Deluxe" cars) have four wheel disc brakes, and they work quite well. In spite of the fact that all of these brakes work well, there is occasional argument (sometimes bordering on religious war) over the need or desire to convert the 1500 cars to front disc brakes. The first compelling fact is that for concours show originality, any of the cars must retain original parts. Otherwise you're free to change pretty much anything if you so desire. After due consideration, I will insert my three cents worth of opinion.

Manual drum brakes in good condition can lock up the tires at any speed (even the sticky race tires). It is just a matter of conscientious driving and heavy enough foot. In 200,000 miles driving MGA 1500 cars with drum brakes, including 100,000 miles of trailer towing (no trailer brakes), I have never rear ended another car. With cool brakes and a single stop, I cannot imagine why there would be any difference in stopping distance between drum and disc brakes (unless you might have some defect in balance between front and rear brakes).

In 10 years of serious weekly autocross competition with SCCA, I have never had any brake fade when doing single laps up to 90 seconds duration. Several years ago I ran hot laps around Blackhawk Farms track (1.9 miles with several turns), doing several consecutive laps at a time aggressively with race tires and heavy braking, and no noticeable brake fade. This would of course be different with higher engine power, higher speeds, and more braking time in competition.

I have been able to make the drum brakes fade in two different circumstances. First was a brisk run down a mountain road with many switchbacks and repeated braking from speed. Second was during a brisk road rally with maximum acceleration and braking for a sharp turn at one mile intervals. The drum brakes began to fade after 3 or 4 consecutive applications from over 60 mph. At that point it is a matter of common sense to slow down a little and use lower gears and less brakes for deceleration.

As an additional minor point, the disc brakes have slightly higher unsprung weight than the drums, which may adversely affect handling when braking on a rough surface. I take that into consideration when autocrossing. For myself, I have never had the impulse to spend the money to convert from drums to discs, simply a personal evaluation of cost vs. benefit. Sometimes "good enough" really is good enough, and maybe we don't need to modify or modernize everything on a vintage car.