Bearings and bolts

[Bison]

Hello Folks,
I've stripped the various engines I now have and will use a K bottom end, when checking the bearing numbers I have a mix of standard spec bearings and C3 bearings.
I have
main crank bearing 6306
g/box mainshaft l/h 6203 C3
mainshaft r/h 6304 C3
layshaft l/h 6204
layshaft r/h 6203
Cam 6202
Does anyone know whether all the bearings should be high speed ones, IE C3?
My other question is should the connecting rod bolts be replaced as a matter of course?, they look rather beefy compared to the ones I removed from my 1977 motor.

Thanks,
Alan.

[Bison]

For info and to answer my own question. All the bearings I removed from my K crank cases were C3, so I assume that;s what the factory fitted.
And that's what's going back in.
Alan.