I’m no expert but here is my two cents…
Try to find a cast iron gearbox housing from an early 95 or 96 with 4speed transmission. They are much stronger, but not so easy to get ones hands on.
I don’t think you’ll need any steel caps or bolts through the bell housing if you use such a housing.
The SSR department sold an even stronger version of the housing. But they are hard to find nowerdays.
The bell housing is not the weak point, it’s the gearbox housing.
But newer V4-models have a reinforced bell housing and a thicker incoming axel, so find one of those. Sorry, don’t know from which year it was fitted.
I have never heard of anyone who needed oil cooling on a V4 gearbox.
On the 99 and 900 it’s common because the motor is on top of the gearbox. But a V4 box does not get that hot.
The freewheel with 6 rolls are stronger than the other model (10 rolls??).
15kg preload on the lsd is quite sufficient.