Ignition coil module suspected faulty, can I switch modules around?

What is worse is that it's already difficult to get replacement modules for 10 year old vehicles. One of the hidden items the automaker EV deal with the feds is that they would stop making parts for the old vehicles! That way people would be forced to buy a replacement vehicle. It's why I have gone out and bought a few parts cars and stripped them for parts. I plan on completely rebuilding one and doing as much rust prevention as possible and having it ready for the future. May even put a couple other vehicles into storage as reserves.

Sort of true, there is an agreement to keep parts "available" for 10 years after the end of production of a vehicle, but there are a lot of exemptions to this as it isn't a law, just a handshake agreement made so auto makers could secure some items in a federal contract.
The only real law is the Magnuson-Moss warranty act, and it states they have to maintain parts availability for the length of the warranty. The other is the emissions warranty for those items covered under it.
That bit Ford a few years ago, a lady had bought a new truck and the heater control head failed real close to the end of the warranty. She went to Ford and they basically said, "Yep it's bad, but we no longer have that part, Sorry" Ford at that time had a real grocery list of options that added different switch options to the panel. The option package she had was like 1 of 10 built. She went to court over it and won, Ford ended up sending the control head to the company that made it and they built 100 replacement boards, but those were equipped with all the switches and became a "universal replacement". The switches that were not needed just didn't have the working buttons in the trim.
It can drive shops up the wall for some things.

There are a lot of those "agreements" in the auto manufacturers world.
If the speedo cable housing is intact you can get the inner cable as a universal item that you cut to fit and add an end to it.

Maybe, the part number there doesn't show exact fitment. The inner cable might be correct length.

I don't show the length or part number in the service information. I don't even recall a 98 as having a mechanical speedometer but an electronic one but it's been a while.

Once you have it rooted out just hit the throttle a few times to blow anything out then put it back together. If you can find a kleen screen gasket for it that would help a lot in case a chunk was still floating around.

See how much comes out but I've seen large chunks a few times. The 4.3 engines were really bad for carbon build up causing the EGR to stick open. Then GM decided to share the misery with other engines.

Yeah, there were a number of different companies that made them, there are also screens that just pushed into the port like a freeze plug. They have sort of gone away because of design changes that deal with carbon better. These days just finding the correct parts can cost you hair! Finding a part that was only made for a specific use can be a real headache.
BUT if you look at the Standard Products VG214 you might be surprised, and if you look at the two in the image, I attached above you might also notice something, IE just because they say it "isn't right" doesn't mean it doesn't fit. GM only used a few EGR base designs.
You might like https://www.3800pro.com/ if you want some "light" reading..

Well, considering it is in their catalog and can be bought for the 3.8 in multiple parts stores. I don't know what they will say unless they stopped making them. But the Dorman one is the same base design.