DEATH WOBBLE AT 40 MPH

I was hopeing someone could shed some light as to why I've got Death Wobble at 40mph after a fullwidth front and rear axle swap?????
Here is what I've done so far.
Swapped in a 1979 HP D44 front and the D60 out of the same truck in the rear. I am running a 3 link Rockkrawler 8" system on my 96 XJ. I've had it professionally aligned after the swap and it's reading perfect. The front measures 5.9/ 6.1 degrees of caster. The pinion angle is better now then w/ the stock D30. I've called RockKrawler and their techs say the 3 Link setup will work even w/ a Front D60 axle swap? So the weight of the fullwidth D44 should not be an issue??? I'm running 37x13x17 tires on 17x9.5 Allied Beadlocks!!

Here are some photos of the setup!!!

I'd start with the wheels and tires. Have the balance checked out. Have you looked to see if you've lost any weights?