Upgrade transmission or what can I do?

[totta Crolla]

Have a look at the Quaife[u:d318775f0c] pro [/u:d318775f0c]Ford type 9 'box as the shafts rotate on needle roller bearings it can stand higher revs than the normal Quaife set.
Expect to change the ring and pinion to something like a 4.8 or ideally a 5.375 to make the most of a close ratio box.
Dogboxes are nice but the dog rings are expensive and need changing at regular intervals.