Rover p6 rear diff

[sowen]

While I'm just about to switch to a lt77 on my rover, I began to think about the rear diff, will it cope with a 3.9 rover v8 and a lead foot? I was wondering if anyone has any experience (good or bad) with the rear set-up on the p6 rover (de dion for those who are unfamiliar with it), and what it is likely to handle before it finally goes bang.

It currently has the 3.08 ratio, which I think will give a cruising rpm at 70 of about 2500. My 3.5 landy seems happy pulling the same speed at approx 2200 rpm. Would a 2.8 ratio jag diff with the inboard discs be a sensible alternative to give a better cruise and able to transfer the weakest link to another part of the transmission? It looks similar in size and layout to the rover unit, and is a proven unit but doesn't have the long drive snout, so would require a longer propshaft and new mountings.

Am I wasting my time looking at them, while the standard jobbie is good enough for what I use it for (occasional traffic light grand prixs, possibly regular trips to shakespeare county)?

I do lots of motorway miles so cruising is far more important to me than acceleration (capacity makes up for it though ). I could always stuff hard rubber on the back so that the rear wheels are more likely to spin up if I press too hard to save my transmission. I don't want to spend too much money if I can help it, and I'd like to keep as much of the standard set-up as possible. Any advice/alternatives welcome.

Simon