It's not going to solve your problem. There are only two way to solve your problem depends on what's the source is.
1. Find another shop that knows how to rebuild your MTX-75.
2. Learn how to drive stick shift.
It doesn't matter how much more power your engine is going to put out, it doesn't put more stress on the synchro. It will only fail if you didn't have a proper rebuild, or you abuse the tranny, or it's just getting too old, or all of them combined.
