Sanding advice needed

Bare Metal...that way you will find all the body work that may be "hidden" With that much paint on the car have you tried using a razor blade to remove the paint? Mine had about the same amount of paint on it and the old paint flew right off down to the original primer....me and my friend had the car down to the original primer in a matter of hours, it would come off in big chunks....but you may not be so lucky. Another quick way to chew through paint is with a DA sander and some 80 grit....that should make easy work of the paint as well....wear a mask.

if sanding, you should use a coarse grit like 36 and slow rpm to avoid heating and warping the metal. I would suggest buying a chemical paint remover instead. you can get them at any auto parts store. They will take care of most of it for you without causing any damage to the metal, then you can follow up with a DA and 80 grit.

80 GRIT always works for me... strippers seem to take forever, especially when you have that much paint. Also just sucks to work with..

If the original paint is well adhered you could just block it and stop when you start to get spots of bare metal. The paint doesn't have to be removed unless there is body damage under it or the paint is peeling. If you just block over the paint you already have it will help to straighten out the panels rather than introducing more ripples for your body guy to fix.

You could also use sandpaper something like a 36 grit on a DA won't warp the panels if you don't hold it too long in one spot or push too hard on the thinner panels. It's a lot of work though and you'll need a lot of sandpaper. It will also require additional body work to straighten out the marks from sanding.

Probably the best way is to hire a pro with a media blaster. It won't warp or mark up the panels if media blasting is done correctly. I realize it costs more; doing things the right way usually does. In the past many times I have done things the cheap way only to start over and fix them. My advice is to take the time to save some more money and then do everything right rather than take the cheap way out. You'll be much happier with the end results.

be very careful with 80 grit or lower. You can erase body lines VERY quickly.

I would just use chemical stripper.

I always use a razor blade scraper first than DA with 80

I did mine with a razor blade

tip, let car sit in the sun for awhile to heat up the surface, it`ll make the paint easier to get off. It`s not near as bad as it sounds.

I went all the way to metal using Mar-Hyde Tal-Strip. I've had the best luck with this particular brand of stripper. The stuff is brutal if you get it on you, but works great on old paint. Just brush it on, let it sit, then scraped it off with a paint stir stick while wet - or if it dries, hit it with a 3M Paint and Rust Stripper using a cordless drill. I ended up going over everything with the 3M stripper, just to clean and shine. I'd clean everything off with a degreaser, then coat with Eastwood rust preventer.

I'd take the time to get to the metal - paint hides a lot of future problems.

The problem with going to bare metal with strippers or blaster is that every dent or ding is now exposed and you or the body man will spend hours $$$$$ applying bondo or filler to flatten every little exposed ding. You should sand off some of the paint to see if there are any rust areas but if there is no surface rust use a DA and sand off until you just start to see small spots of bare metal. Those will be the high points and you stop at that point. The old cured paint makes a good base for primer and after sanding the surface should be perfectly flat. You MUST treat any suface rust areas to remove rust or the spot will rust thru the new paint in 6 months.

If you leave your sander flat you wont hog out all of the old bodywork, but it will allow you to see where you have "dings and dents" had I not gone down to bare metal I would not have found that my drivers rear quarter had bondo nearly half an inch thick in it. Also found that my passenger door had been beat up pretty bad as well. I understand what you are saying, but if you want something to look "right" you need to know what you are working with. With a 40+ year old car, you just dont know whats beneath that paint.
On these old cars, the main thing that needs to be straight is the hood and rear quarter areas. DOnt get me wrong, you want to find that the whole car is in good shape, but everything else can be bought and bolted on (if necessary) at a reasonable cost...no body man required (provided you buy quality parts) I bought new fenders, valences, hood, trunk lid, passenger door all for my car for about 1400 bucks....would have paid a body man 2 or 3 times that to "fix" the other ones.