Its not really that expensive to get a diff shortened, i'm putting an SR20DET in my 120y and i'm using a cut down 28spline r31 diff. Its going to be plenty strong enough, i'll prob keep it open for a little bit, until i can afford an lsd

I'm getting my cut down at DR Datto on the gold coast, they're good and they don't overcharge like some places do.
I only paid 100 for my diff, i had to pull it out myself but i got all the handbrake stuff, discs rotors etc plus i got all the control arms and stabilizers etc that i'm gonna make into anti tramp bars.

Also doesn't topgear make LSD's for h165? all alloy too i think?

Hope i helped a bit
Ty