Whats the best choice for rear diff?

We're using a Fireblade engine and have been told that we really need a limited slip and also that the best gearing for these engines is around 3.36:1

I've got a standard seirra diff which is 3.62:1 and not limited slip.

I've seen a re-con diff thats 3.36:1 but its not limited Slip.

I can get hold of cossie parts fairly easily but dispite being limited slip they are 3.64 (2wd) and 3.62 (4wd).

What do I go for without spending a fortune on a Quaffe?

What have others used?

The diff is either limited slip or not, but it is the crownwheel and pinion that set the overall ratio. You need to speak to a specialist rebuilder about the possibility of combining the parts you have got and can get to produce what you want.
Westfeild people use-
Phil Stewart at Road & Race Transmissions on 01959 525105 based nr Sevenoaks in Kent

John

just spotted an advert for diff and lsd doings for westfeild etc in Kit Car no name given just a number 01380 812969 (Devizes Wiltshire)