It wont fall apart every 6 mos. The gearbox you have is more than 30 years old and was factory fitment for high-torque A15s ... New rebuild kit is about $250 or you can just buy the synchros for $100 or so. Most likely only a couple of synchros need replacing

That being said the T50 is a bit stronger, so if you are doing drag starts, maybe it's time to upgrade