puchfinnland- Yes it is possible to remove the old drop outs and relplace them with cast or forged ones with a der hanger. The process is filled with issues though. Finding a pair of drop outs that mimic the shape/dimensions of the old is the first step. Specificly how the chain stan and seat stay line up with the drop's tabs (don't even think about socket or plug style drops!). Assuming that the drops' tabs are long enough and about the right angle to match the old then comes where is the axle compared to the old. Some minor change of axle position is common but too much and the bike's handling will be different. You'll want to retain the traditional slotted style, no verticals.

The actual installing can go one of two ways. The best way to maintain the handling and dimensions is to do one drop at a time. Using the old one as the guide for the new. This can be done with a good builder's wheel, good drop out match up in shape and dimension so that the stays don't need much work to fit the new drops and simple set up. Remove one side drop by cutting it in half and heating one stay/drop half at a time until the drop half falls out of the stay. Repeate for the other drop half. Clean up the stay ends, fit up the new drop using the wheel to hold the drop in place (mimicing the still in place old drop). All fitting should be with out any stress or clamp induced flexing to the stays, it's REAL easy to have the stay end crack and split during brazing if the fit up is forced. Once the first side is in place repeat with the other side. If you've been a good boy the wheel is in the same place it use to be and well aligned with the rest of the frame.

The second method is to not be worried where the axle ends up (or jig up the frame to record the axle position) and remove both sides at once. Then do all the same fit up with the new drops, care taken as discribed above. With out the old side acting as a locator you will be deciding where and how well the wheel is aligned (easier with a jig that the old set up was saved by and the jig now used to hold everything in that same and straight place). This method can be faster if you know what you're doing, but if that were the case you wouldn't have posted the question...

Replacing drop outs can seem easy but get you in over your head quickly. Andy.