What about the pressure plate and harmonic balancer pulley as well as replacing the water pump with a forward rotating water pump in place of the serpentine one?

Sorry, too many changes between the old and new motors.

Most of the 400 is are externally balanced, while the 350 is and 327 are internal, so no on the flywheel and balancer. No on the waterpump too, the rotation will be backwards and wont cool it properly.

good luck

Are u converting the Vortec to a carburetor? If so, u should be able to use the old style balancer, but u will need to use an old style timing cover as well for the right timing marks. You can not use the 400 balancer or flywheel because the 400 is externally balanced by the balancer & the flywheel. The 350 is internally balanced.

The water pump & pulley setup from the 400 should work fine. You will need a flywheel for a 1 piece rear seal engine because the flange & bolt pattern is smaller for the Vortec engine. Your old flywheel wo not fit. Also, u will need an electric fuel pump since the Vortec cam does not have an eccentric to operate a mechanical pump & the block is not machined to accept one.

The Vortec is a standard small block once u strip off all the electronics & fuel injection parts. You will need a Vortec style intake manifold for a carb. The short block is basically the same from the mid 1980 is & up, so u will need the parts from this era to complete the swap.