Re: 6300-6314 D&RGW flats

According to the Colorado RR Museum plans,
6200-6219 had cut down S.G. steel bolsters, steel draft gear, wood sills with steel angle reinforcing on the center and side sills. They are 36' long.
6300-6314 were all wood with the only steel reinforcing being the rail on the side sills. They are 40' long. The draft gear appears to be wood and the body bolster appears to be closer to the 3000 series box car style.
I recall an article in 1978 MR about the D&RGW gons and all the underframe variations. The difference between the 6200-6219 series and the 6300-6314 series may be the length and the slight differences in the bolsters and draft gear.
Thanks.
Doug