the only time your standard strut rod has an impact on castor its usually not a good imapct, and i think its due to the use of the wrong strut rod bushings
one combination of early and late parts puts too much bush between strut rod and rear of k frame
this means the strut rod sits a bit further back and pushes the lower arm back a bit
and makes it much harder to get any + castor.
i can't remeber properly what the diference is
but there seem to be 3 styles of struts
threaded end for use with a split pin: short thread to collar
threaded end for use with a split pin or nylock nut: long thread to collar
threaded end for use only with a nylock nut : long as above (no hole for split pin)
i thnk the position of the collar moved slightly to get more rubber in to reduce noise and vibration
short means some time in the 1960s
long appears to be late 60s onwards
both of the LONG can be used with multi part bushes that have a steel centre sleeve i.e moog upgraded version
i think the "short" can only be used with the 1 piece bush or an after thought/aftermarket multi part bush specified only for those models
I might be wrong... on which way round it all is, but there are subtle differences between different ages of A body strut rods and some combinations do not work as well togther, but they all bolt up if you have a big enough spanner.....
dave