Rusted out push nipple on 80 year old cast iron radiator

I'm seeking two replacement push nipples for this historic radiator. I've contacted Oneida County Boiler Works who has a push nipple in the correct diameter and thickness but the length is 3/16" shorter than the original, 1-5/16" vs 1-1/2". Can we use this replacement without the radiator re-leaking over time or does even a 3/32" shorter difference off of either end affect the taper too much and make it too risky to try to reinstall? If so, does anyone know how or where we can get the exact size replacement push nipple? Thanks.