I inherited a 67 250 and a 73 250 from which I built up my present engine, 73 block with the 67 head. Both engines were complete when I got them and both upper alt arms were the same. They may have come in different lengths for other years or applications?
I had a clearance problem between the alt and the front tube of the Clifford street rod headers if I tried to use those brackets - not enough slot to get the alt away from the header tube. What I did was cut them apart and welded them back together so the longest section of each was used and that made the new fabbed arm longer than it originally was and moved the alt further out away from the header. If you are looking for a longer arm for a similar reason this might be something to think about or else a trip to the salvage yard with a tape measure might turn up a suitable arm without any fab work.
