stock 1969 340 dart wheels
Those were made by a guy in the Northwest. They are SBP centers with 15" hoops welded on and powder coated. The BS is either 4.25 or 4.5", can't remember.
You're not the first one to do this. The guys who make these wheels know what fits, as long as the car is stock. (stock rear end) They were ~$100 each + shipping.
PM me if you'd like his contact info.
PK