F15 5th gear gearing

[AMQR]

Hi all, I'm looking to gear up my x16xe corsa. My problem is when i'm sitting at 60mph shes turning over at about 2900-2950 rpm and when i'm go on up to 70 80 90 shes crying out for another gear lol.

Don't want to go down the line of any F13 if possible. Was thinking about a F15 C355 from SOME early 16 corsas and SOME mk3 astra 16 16v's but there as rare as hens teeth!!

I'm now thinking of changing the 5th gear from current F15 33T to a F17 31T from a Y17DT or Z18XE mk4 astra with F17 W355 or even the 29T fitted to ECO Z17DTL models but it may be too high geared and bog down when changing from 4th up!

Just wondering would the F17 5th fitting on to the F15?

And is 5th gear at the very outside nearest the cluster cover?

Thanks