Rivetmageddon...

Before you start it seems a little daunting but once you get into the swing of it its surprising how easy it is. To start with, drilling out pop rivets is a doddle; their central pop hole means the drill is always perfectly centred and it takes very little pressure before the drill pops the back off & leaves the inner flange spinning on your drill bit - you'll soon find you have dozens spinning on the drill bit. They're sharp - use a pair of pliers & run the drill in reverse to get them off.

There are two (well I'm sure there are more but two will do for now) things you don't want to do: Enlarge the original hole or follow through to such an extent that you end up drilling the outer skin.  To avoid enlarging the hole, get comfy and drill straight, use the right size of drill, or slightly undersized. I found a 3mm was perfect. I'm pretty sure that they were 1/8" (as are the solid rivets on the exterior) which is 3.175mm in metric.

There are commercial drill depth-stops but I found using 1" gaffer (sorry, my profession - you'd call it duck tape) tape wrapped round the drill bit (to about the thickness of a pencil) leaving about 3/4" of drill sticking out, cushioned any follow-through perfectly.

Solid rivets are a little trickier.....The Bucked rivets were put into a 1/8 hole (or 3.175mm) but I think most people rebuild using a 5/32 (3.969mm) Universal solid rivet which needs a slightly larger hole, so you could use a 3.5mm drill bit but I find a 3mm popped them out fine. You'll find you have bucked rivets down the side of the door. Mine had a tiny dimple in the head but I wouldn't trust it to hold your drill bit. Use a sharp centre-punch and a sharp tap & you'll have a good centre guide that the drill won't slip out of.

The last sheet comes free and despite being bent for half a century they spring flat like a new sheet.

Perfect templates - though these are fine & will go back...

... and a half-stripped interior. Since we plan to lift the body off the chassis I'm going to leave all the upper interior panels in place to help (along with a lot of wooden bracing) her keep her shape. I was prepared to get through lots of drill bits but this only took about 6. They get blunt & hot (which makes them more likely to snap), so change them when they're not cutting as well. I reckon I'll need quite a few more to drill out the solid rivets on the exterior.