Hilux diff would be your best option, however an LSD will set you back a bit.
A commo diff would be cheaper to purchase initially, but they have to be cut down as they are too wide. Then custom / shaved axles. $.
And a T-18 diff is almost the same as the diff in your RA28. There are only external differences such as mounting points. They are both T-series Diffs, so neither one of them is going to be stronger than the other, and they will not hold up to an SR.
Go hilux and don't look back.
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