Sm or Lg case 4.10 LSD for M42 best?

[UpOn3]

hey guys, I'd like to replace the small case 4.10 Open diff in my 91 M42 with a LSD unit. Which is better, the lighter small case unit from a M10 or M42 or the stronger med case unit from an M20 E30 Auto? Is the Med case more durable? overkill? Is it worth the 20 extra pounds of unsprung weight???

Is it difficult to find a small case unit compared to the Med case unit?

Thanks.

[MR 325]

The medium case diff is definitely stronger and also usually easier to find.

If you plan to stay M42 powered I would just buy whichever diff you find the better price on.