I want to have the car repainted in the original colour without removing the engine or the interior. According to the body shop it's possible that the paint will peel off after some time because of the incompatibilty of the new and old paints. The car has been repainted before but the green the PO used is not the original Palma Green and there are some dents and scratches that need to be removed. Rust is not a problem.
So how do I remove the paint? (chemical paste, sander,...)

Start with a paintstripper on a small patch behind a bumper or similar to see it it works. On my car the stripper only worked on some areas. Where it doesnt work you'll need to sand it down.

Paint strippers of today are weak, and agree you might not have good results. Try different brands. Kleen Strip Aircraft Paint Remover was recommended to me by a body shop friend but haven't tried it yet.

An orbital sander will take paint down quickly, but be careful of any existing filler that might be under the paint as the sander will cut into the filler quickly.

I hand-sanded it off.

A DA sander with 36grit will cut down the big stuff and then 80 grit to bare metal. I can strip a body panel to bare metal in an hour tops this way and your not etching the metal with chemicals.

here is mine back in 1992

Click to view attachment

I have seen a commercial about a company that franchises some equipment that comes to you and strips the car on site,..check U-tube for demonstartion. Sorry I cant remember thier name right now.

If money was no object, you could use CO2 ice blasting.
It leaves nothing behind except the paint dust that was removed.

The "old" Jasco paint remover worked like a miracle and would strip paint off the car to bare metal in seconds.
The new stuff is not nearly as aggressive.
Aircraft paint remover is the best that I have found recently.

Cutting grooves in the surface of the paint by sanding a little, then applying stripper works pretty well.

Cover the stripper with saran wrap so it does not evaporate right away.

It is messy, but I got 7 layers of paint off my car this way.

John

Is the CO2 blasting the same process as the Dustless Blasting that's advertised on My Classic Car with Dennis Gage?

No it's not. Dustless is using water and a abrasive compound, I believe it's baking Soda.
Hence, it's a mechanical stripping.

CO2 is frozen and once it's hits the surface the CO2 is vaporized at impact and the "blast" lifts of the paint.

IIRC, CO2 will 99% only attack the paint, whereas DB has some abrasive "touch" to it but will not remove rust.

I have found that the Norton rapid strip wheel on a 4-1/2" grinder works amazingly wheel. I did a wheel well and the outer fender in about 15 minutes.Click to view attachment

Agree
https://www.youtube.com/watch?v=3oiPw0hsJKM

Do these Norton wheels come in various "grits"? My tub is largely stripped, but I've got a bit more to do to completely clean up the body before I can really evaluate the metal work necessary. My concern is the possibility of removing metal with the paint. On my driver's side front fender, I can feel ridges on the bare metal where a PO apparently used a pretty aggressive paint removal method and took some of the metal with it.

The blue one is softer the Orange one is much more abrasive.. I also have a black one from klingspor that looks to be very aggressive. I will use that underneath.

slotty008, I'm not sure you need to strip the car. If paint now is good and not peeling, sand and fix scratches/dents then reseal and finish......Best, Mark

I don't know how long the actual paint is on but it must be at least 5 years, and it's not peeling. But the guys at the body shop say that if it is cellulose paint it wil react with the new paint and peel off.
Also I don't know how many layers of paint are already there. Is there a way to measure the thickness of the paint?