randemon has the right idea.
I have 3 Flathead V8s. They are not worth the trouble, unless a person wants something original in an old Ford. The cost of rebuilding an old Flathead is shocking and all a person gets is a nice sounding engine that is not very powerful. I spent $15k on my Flathead to bring a little performance into it.
I do not have a good reasons to keep a Ford Flathead V8 other than I like the look and sound and it fits my 1940 Ford. I looked at the Flathead as a base to build something interesting on. If it turns out that I do not like the Flathead, I will change it out for a new Cummins R28 crate diesel engine. It is only money.
https://www.cummins.com/engines/repower The Cummins R28 crate engine is complete and will fit nicely in an Old IHC pickup and a 1940 Ford.
I built and drove an R120 for 20 years and 225,000 miles. The running gear was 100% nothing original. Nothing was lost in the special feeling some persons are looking for. I put a 6.9 V8 Diesel in my "R". There is enough information on this truck, on this forum.
70 - 80 years ago there was a service station every few miles, because there was a need for the service. My family had one of those service stations.
The engines of those by-gone-daze needed lots of service and fuel. From the second a person starts one of these old points ignition systems the parts start to wear and go out of adjustment. A carburetor may be perfectly in adjustment in your shop. If your drive has a significant altitude change, the carburetor will not be at it's best in a few miles. Those clattering valves can be set to specification and they will also wear out of adjustment as a person drives.
I think IHC would have built better if the technology was available to them, for a price.
I am firmly on the side of making my IHC better while preserving the look.
WEW51L110 has it figured out. HIs IH truck has the look, the feel and gets the attention he deserves. I respect what WEW has built. He is driving while others are stuck in a shed worrying about keeping it all original.
Do what you think is best for your situation. If anyone thinks they will save money with a proper rebuild of and old IH motor, have a seat. The $$ shock will knock you over. All original does not protect a person from what they do not know.