Sorry to revive a zombie thread, but...
I absolutely despise the tallness of the 3.40 1st gear in my m5odr1HD (I despise the reverse even more so, but I think I'm stuck with that) so I'm considering options to remedy.
It seems pretty plain from this thread that a R2 swap isn't feasible, and it would seem that parts interchangeability between the 2 is basically non-existent.
is the actual gearset from the non-HD weaker? I'd love to swap 1st-3rd if reasonable, but I don't want to leave myself more vulnerable to catastrophic failure. It is just a stock pushrod 4.0...