Hello ThirdGen, this is my first post here.

I am considering buying a z28 with 300k miles on it. The body and interior are in pretty good condition. My question is how much of an issue is the high mileage if I plan on replacing essentially the entire drivetrain, suspension, etc.. down the road. Are there are things I should be worried about at this kind of mileage such as issues with the frame or anything else I may not be thinking of? Basically I'm wondering if there is a point where the car isn't even suitable as a project. What not so obvious signs of trouble should I be looking for, the car has never been in an accident or had major issues according to carfax. This will be my first project car so I'm far from an automotive expert and have no experience with very high mileage vehicles.

 

The answer is yes. 3 major places to look.
1. Check the area the steering box bolts to for cracks of deformation
2. Pull the seats,carpet and center console and look for cracks on and around the transmission tunnel and for rust on the A-pillars (what the door bolt to)
3. Jack up the car and look at where the transmission cross brace bolts to on the chassis. Check for cracks here also.
those are the 3 major areas I have see crack on high mileage cars over the 23 years I have been playing with them.
all these areas can be fixed but if the car had all these problems your best bet will be to move on and find a different car.