so the engine is out of the van and I'm playing happily unbolting various bits from it and cleaning them up (eg water pump, thermostat housing, timing mechanism etc).
I'm keen to retain all the original bits I can, down to the washers if possible! but I am hazily aware that there must be some bits which are placed under strain, torque or other pressure and which it would be a sensible idea to replace. I'm thinking maybe head nuts and studs, for instance.
Can anyone tell me whether this is right, and if so which fixings I should be replacing rather than restoring?
(I'm not doing anything to the main block of the engine but 3 of the head nuts do have to come off as they need longer studs.)
Grateful for all advice!

juliet xx