Hello,
I'm currently in the progress of restoring a 351w, plan is to change the top end and get 400-500HP. Bottom end has to stay stock though, but i am still changing the bearings now that i have the engine totally apart.

However, i do not know if this is the original bearings? what does the numbers mean? can anyone tell me?

Main bearing: https://i.imgur.com/F60q0SS.jpg
rod bearing (where attached to crank): https://i.imgur.com/KZJ1O36.jpg

I'm almost sure that the main bearing is stock, but the "10" on the rod bearing might make me think that this crank or rods are no longer stock size. anyone know what the "10" means?

The block is from 72.

 

.
the 10 is not the size . . those look like stock size ford bearings to me.
undersize bearings will have a 0 before the number .010 .020 .030 etc.

 

Thanks! just ordered the stock size clevite 77

 

well i hope your crank is perfectly smooth.

also, i would check the clearance with plasti gauge . . if it is a little too much, you can get bearings that are .001, .002 and .003 over size.