PD4104-931 was delivered new in March of 1954 as fleet number K-1872 to Pacific Greyhound Lines, based in San Francisco, CA.
Back then, Greyhound kept their coaches about 10 years, so it would have most likely have been sold off after the summer season of 1964. So, for at least the first 10 years of it's life, it had decent maintenance.
No info on subsequent owners, sadly. . .Paso -
6V71 with a V730 was a common application by GMC in their transit bus line. Decent performance and fuel economy in transit use - but with the 5:38:1 axle. Acceleration and hill-climbing will be sluggish with the 4:10:1 axle.
Why do a double swap? If you're going to install the V730, just make one swap and include the 8V71 at the same time. . . then your bus will run real nicely.
FWIW & HTH. . .