My gearbox always crucnched a bit, specially into second. But after a thrash on corrugated roads refused to go into second from third (or above) unless you double declutched and revved it really hard. First to second was not great but generally worked. The advice I got was that replacing the synchros would hopefully solve the problem.
I'll see if I can get out to Pick a Part tomorrow. btw what was an AE71? Similar to a T18 but with a 4A?