If A Car From 1940 Is Modified To To Use Today's Gas Will It Lower The Value Of The Car?

This is a 1938 Ford Eifel I believe from someone's Flickr account.
I asked a question about it being able to use gas from today's pumps and I got some great answers.
I don't know much about cars other than driving them and collecting pics of them so when a user said it would have to be modified to make it work another question popped up in my head.
When cars are rebuilt to classic status do you lose some of the collection by modifying it?
I know sometimes a part that can't be bought has to be made so does it detract from the value of it's antiquity.
If that's a silly use of the word I apologize but I do like asking questions so bear with me.
Thanks and thumbs up to all who answer… Just give me time to get back and read the answers. Added (1). I meant that to read:
When cars are rebuilt to classic status do you lose some of the collection (value) by modifying it?

In my opinion No,

Up grade to unleaded it. Called moving with the times,

Great car through it looks fantastic

Definitely No, because antique car of 1938 can't be brought on the road because of gas problem. If you modify it to the modern gas so the value of the car will further increase because now this car is in running condition. You must go for it's modification.

It is no big deal to up-grade a car this old to run modern gas! The use of high octane gas was a late forties into the seventies thing. It just takes different gaskets in the fuel system and a different material for the fuel pump diaphragm. None of these items will detract from the value of the car because they are direct fit and match the original except in material!
The timing might need to be adjusted to a different timing mark and maybe a fuel additive used as a lead substitute. There's no continuity or total agreement on if an additional fuel additive is needed.
I see antique cars like this that are drivers. There are car clubs that hold long distance rallies that run modern fuel in original equipment vehicles like this. So it is not as difficult as you think!