What size grease zerk goes on a front driveshaft

[Abloy356]

I just picked up a junkyard front shaft, by the part number/length its a 89-01 4.0 auto one to use with the IRO hack and tap I'm about to install.

Unfortunately, its missing the grease zerk on the slip joint. Does anyone know what size that is?

[4.3LXJ]

There are only two "sizes" for the small zerk fittings and they are 1/4X28 and the metric equivalent. Almost certain it is a 1/4X28