Is the gasket between the upper and lower intake manifold usually able to be reused? Is this a must-replace item if the Upper and Lower is separated? Just trying to gather all parts at once for the project. Often times rubber gaskets like that can be reused but other times they take such a set that the elasticity is lost and won't seal properly again. Any experience with this? I was already advised to use the Fel-Pro gaskets on the lower intake so I have those on the way.
Fel Pro gaskets MS98000T

Part number 6
https://www.mercruiserparts.com/bam/.../31849/8093/90

The MS98000T set has the upper gasket in it. That is "assuming" it is the same as the truck one. You definitely should replace the lower bolts. Use the GM ones from the dealer. And you need an inch pound torque wrench to do the job properly.

Good to know, I will be getting the GM ones. Having trouble finding the Intake in stock.