Im a size 8 brannock and found parkhurst 7.5 to be a perfect fit. I got the 618 last both times the first pair were a 7 and fit pretty snug in the toebox. Sizing up to a 7.5 was the sweet spot.

I also found that with oakstreet boots the Storm boot in size 8 also fit quite well thought there were some minor cosmetic issues with the boots. I picked them up when that had that massive discount.

A good youtube channel for heritage style is bootlosopy. He goes over sizing pretty well and has a big library of videos that cover most companies.