Posting because these engines, like most good things, are long before I was old enough to care that a Choo-Choo doesn't always go choo-choo...
As a side effect of a post in another forum on this site, I am wondering about how EMD engine models overlapped. In particular, the GP7 and the GP20. According to Wikipedia, the GP7 was built from 1949-1954. The GP20 from 1959-1962. So there's five years that they don't overlap in PRODUCTION. But what about hauling goods on the rails? Did the folks who had the older models immediately try to trade up for the better performance? Did EMD kinda talk 'em into trading the used models in for the brand new, red hot goodness? You're still talking about the 567 engine, both with the V-16, but the GP20 was turbocharged for an extra 500hp.
Would you find lash-ups made this way? Could they be made this way? I don't even know if there are rules about this sort of stuff (like not dating your best friend's ex-GF or marrying your 1st cousin). Somebody please educate me!
PS: Technically, it doesn't matter. The livery that everybody seems to know came into reality in 1974, so all of those early GeePs were probably long gone and certainly would not be sporting the newest colors!