Re: Looking for valves, fittings cast iron radiators
If I'm understanding, the problem would be that the different elbow length would interfere with placing the radiator because the hole in the floor would now be off position by some fraction? So either enlarge the floor hole where it is (if in a slab this would be intractable) or borrow an old elbow from another location where altering the floor hole would be less of an issue. As hard as it is to withdraw these old fittings (even if they are closer to 100 years of age than 200) it makes it a riskier option.
As a last resort, maybe something could be cobbled together out of fittings, nipples and elbows and a union. (oh my!)
Remove not the ancient landmark, which your fathers have set.