But of course the suretrac can be mated with any ratio . I think I still have a Subaru Suretrac unit in my shed . I run a 4.11 ratio diff . There were also two versions of the viscous Subaru units . One standard diff with a thin viscous unit and two Spider gears and one stronger diff with a thicker viscous unit and four spider gears . 

Thankfully with making the conversion kits for years I have a few suretrac’s on the shelf though they are always in 4.11. 

You were very lucky to find an AP Suretrac . Very rare . An amazing piece of engineering . I have some pics on my phone . I’ll post a couple if I can find them .

Small update, i have built a hybrid R160 rear diff up. Using a 3.54 open diff and a 4.111 apsuretrac to give me a cheapish good ratio torsan diff. They are fairly bullet proof and wont suffer from the same  issues as the viscous LSD's of the fluid aging.~ Though probably should have baked and painted the casing before assembly 

Ok they arrived today which was superfast. First impressions are that they feel super light and well made. Over 1kg per side saving which is a huge plus on unsprung weight. I have compared them to a spare Gt6 hub. (I removed the bearings and races and stubs though a small amount of grease remained. The inportant bearing dimentions are identical so big win there as well as a 1.1kg saving per side. However the bolt holes for the disc are not taped like they on on the cast iron one and the stub holes have no groove marks in (though i guess with it being ally once they are pressed in they will form their own. The centre of the hub also doesnt have the same big void the stock one has. The rear of the hub doesnt have the same external step in however i cant think why that would mater.

Can't you just cut 3inches off the long one? 

Not that hard to make the collector…… …… for a man of you talents. Just saying   

Thanks Ian. Happy Birthday. Hope you get out on the bike today. And manage to keep the faith with the Sprint

Brilliant.