I'd compare the tube diameter of the new pipes that don't, and the scabby one's that do. So if they are the same, the fault lies within the ports, exhaust sealer and coke masquerading as cast iron.
The A7 and A10 castings are almost identical externally. It would make economic sense to use one size of tubing, and from experience an A10 pipe will fit into an A7 head and so I know the ports are the same size. Plunger head casting numbers are on the underside of the inlet manifold, wide fin heads have it stamped or cast on the underside of one of the bottom fins.
The claim for fit sounds the sort of advertising copy from a supplier local to me........
Swarfy.
Additional. Here in Suffolk it's a lovely day.