I noticed that some RS-3's have their lights vertical and some horizontal . Was this up to the railroad which way they wanted their headlights ? or did this happen while being rebuilt ?
A subject close to my heart! There are a number of other unique details to the groups of RS-3s on the Reading, but we'll start with the headlights.
You have to realize that the order that they were DELIVERED was not the number series! It seems that the Reading was trying to figure out its roster, especially around the time the RS's were delivered. In fact, there was a note from E. P. Gangewere, head of MP&RE, stating that there was sufficient room in the roster for units being delivered. Such was not the case! They were starting to run out of RS-3 numbers, and would be bumping into the AS-16s numerically. Here's how they were delivered, and the headlight configuration:
500-509 (4/51) old style, single-beam headlight
510-524 (7,8/51) twin sealed beam, horizontal
496-499 (4/52) " " " " " "
473-475 (4,5/52) " " " " " "
460-472 (5/52) " " " " " "
484-485 (6/52) " " " " " "
486-495 (6,7/52) " " " " " "
481-483 (8/53) Twin sealed beam, VERTICAL! AHA!
444-450 (12/53) Twin sealed beam, vertical--these also had larger fuel tanks, and were used on the Grace Mine Runs mostly
Pretty wild, huh?
AT LEAST one (maybe others) exception: 519 had horizontal twin sealed beams, but possibly a headlight plate from a Baldwin AS-16, probably after it was scrapped.
Apparently, it had to do with when the units were built, and what was in fashion at the factory. The Reading was very conservative about changing things around.