Roop, as I said in the last thread in which this topic was mentioned, the box can be made to fit, but it will have the wrong gear ratio.
All M5s and every 540 that I can think of are factory fitted with servotronic.
Again: every model with one of these boxes uses a different gear ratio. E.g., E32 750 isn't the same as what's found in the E32 740, and from what I remember, none of them are interchangeable/will retain the stock driveability.
Personally, I think servotronic is an unnecessary option, and probably not worth the effort of installation in a non-servotronic car. It'd be wiser to buy that box at the ridiculously low price it was offered, sell it on eBay, and then find a low mileage m50 525 box to replace your existing unit. Of course, there's always the possibility that the imprecision is due to bad links, universal joints, or other variables in the system, making the box replacement unnecessary.
best, whit