In the realm of front suspension pivots, there are places where urethane might be beneficial, but there are also places where rubber is better, by observation.
To me, the UCA would be a good place for urethane as that's not a big place where impact absorption happens, just pivoting to keep everything in place. The LCA would be where rubber might be better for impact absorption. BUT if you look at some of the old "Road and Track" vids on YouTube, it becomes obvious that the UCA is where a lot of the wheel lean during hard cornering might come from, too, at least on GM cars and their worse camber angles than anything Chrysler usually built back then. So, keeping those UCA bushings "tight" would be good.
BUT the LCA is also more important for steering accuracy. BUT how many times in normal driving do you really need laser-accurate steering in a system that's got so many greasable pivot points (and possible linkage rod flex) in the linkage? IF you were auto-crossing or racing at 3-digit speeds, a different situation. Where a .5 degree difference in total response could be significant in a competition environment, then the least deflection is the best.
Also, there are ways that road racers used to stiffen-up their rubber bushings, before urethane was used for that purpose.
CBODY67