wrong idler arm

i think i may have the wrong idler arm on my 73 duster car has power steering and currently has a 400 in it originally a 318. every idler arm i order form which ever company is wrong ive tried a year earlier and a year later and obviously the 72 is wrong and the 74 is the same as the 73 they send me down. do you need a different idler with the big block swap? i didnt do the swap is this a manual. the bushing lines straight up with the pivot
thanks in advance