low mileage 360 teardown explanation ?????

I Just purchased a 71 360 out of a c body, very low mileage n seems very original. Here are numbers out side n inside. GW360R3618- frt. of block, pass. side, 5-27-71,dri side, 3418496 2 360, crank-3418640-1,rods-3418645- KRY,KLJ,KNL,KNG, two different colored rods??? a 2 copper colored the rest standard colored ??? pistons-3418919 09104, main caps are stamped-5-9-71. Could some one explain the rods n different production dates ??? it was very clean and very even bearing wear all around, the cam bearings were faking pretty bad. Pistons are flat tops.