First, not all 3 piece cores were equal. That went clear back to polyester era. Columbia high density weight blocks gave a superior reaction to Brunswick and Ebonite 3 pieces blocks. By the time urethane came out, the AMF Angle also employed the high density weight block. Despite poor quality control, it was superior to all the other urethanes until Columbia came out with its U Dot series ( wine and black ). By this time Faball did revolutionize cores with its 2 piece ball. Although very high rg by todays standards those 2 piece balls were lower than the 3 piece balls, plus they had differential which produced flare and for the first time dynamic balance rather than static balance became a factor.
When it comes to surface, it should be remembered that the predominant oil pattern was extremely short during the 80's at 24 feet. All urethane balls came with very aggressive surface prep compared to todays balls. The most successful ball of the 80's ended up being the Blue Hammer which came at 400 grit from the factory. I don't think any balls came rougher than that from the factory, but guys did take them down as low as 220. The problem with the urethanes was two fold. They needed the strong shell to hit, but the lane would polish the shell up above 600 in no time. In addition urethanes soaked up oil which altered the shell and kept the ball from being restored to factory, even when the 400 grit was applied. the result of these two factors was that carry down was a huge factory on the fresh patterns. While lanes were only oiled 24 feet, the heads were flooded, and there was no buff out. Anything other than a top hat wall became very difficult in no time. As an aside, that is where today wet dry top hat pattern came into vogue. Prior to the 80's lanes were walled, but there was much more of a taper out to the edge as opposed to a wet dry oil line.
