I need axle bearing info for my 12 bolt

[tranz am]

I'm currently working or narrowing my frame and my 12 bolt. I have a couple options for axle bearings to chose from.
I am going to be using 1 of 2 Moser housing ends. I can use either the large ford style press on bearings with housing ends and custom order axles for $380 a pair, or use The 12 bolt Car ends that use the smaller bearings with ends and buy direct fit 1967 nova axles for $260.
The Nova axles are the correct length and spline for my application.
I would rather use the small housing ends if i can get away with it.

My question is when do the smaller bearings start to have issues? I'm guessing they are fine to use up to a certain speed and load but where that point is I'm unsure . Thanks!