Absolutely do not get the poly offset bushings, they are awful! I had them in for 6 months or so and they were so much worse than the stock rubber bushings it was scary.
To quote MM's website...
"We don't recommend offset rack bushings for stock K-Members...
Offset steering rack bushings move the rack far too much on stock K-Members, and make an acceptible situation far worse than if you had done nothing at all. See our test results in the July 1993 issue of Super Ford, the September 1998 issue of 5.0 Mustang."
When I switched from my stock rubber bushings to the offset poly's my tramlining definitely got a bit worse and there was really no more of a positive feel to the steering. The problem with them that both of the articles discuss is that because the bushings are free to rotate in there, they will rotate to the left a right a bit when steering forces are applied much like the stock rubber bushings squish to the left and right.
The new style MM solid bushings have a spherical bushing on the back that allows the steering rack to move with the k member when it flexes, but it does not allow the rack to move left and right when turning forces are applied, that is why it reduces tramlining so much and gives such a crisp steering feel. As long as you still have a stock steering shaft, the rubber rag joint bushings in there will eliminate any and all vibrations and harshness from the steering, I drive my Cobra 20,000+ miles per year on horrible NJ roads and my MM aluminums have been the best mod I've done thus far, they are absolutely flawless.