Hi Doug, great to see a younger bloke into early Holdens.

Without knowing anything about the state of the 253 engine you've mentioned, I'd reckon stick with a Stromberg - particularly with economy in mind.

But my 20.2c - work with what you've got. By the time you've bought the parts and done all the work to remove the 202 and change to a 253, what you're going to be left with is a 253. Nice and I reckon cool where its a original fitment, perhaps a bit of a waste of time if you could put something better there later on.

Having owned cars with either engine, if both engines are in equal condition there is zero real world advantage to a 253 over a 202 other than exhaust sound.

When getting advice on the internet sometimes its about how much information you give. For example, the real costs for ownership of making your ride a comfortable, reliable daily driver you'll be happy to get around in is much more about the condition of the rest of the car than the size of the engine and the relative costs due to fuel economy.

First thing - does the car leak and what rust are you dealing with.

Then just some other examples - a major mechanical service so you can rely on it, a nice set of wheels (even just nicely painted factory stuff) and tyres, suspension (maybe a few bushes gone? shocks?), interior tidy up (carpets, seat belts, music, tint, etc.), find a cheap power steer set up on ebay, etc. etc.

Good luck mate.