according to this
https://en.wikipedia.org/wiki/Straight-eight_engine
the firing order is 1-4-7-3-8-5-2-6
which is not described as any specific engine, only the gif.
but the only one that pops up with that one in a quick search is a Caterpillar engine (!?)

however, I found the Buick is 1-6-2-5-8-3-7-4
https://www.jalopyjournal.com/forum/threads/buick-straight-8-firing-order.382117/

and Packard is
1st and 2nd Series Packard Eights (1923 and into 1926) 1-3-2-5-8-6-7-4
later Packards "There are VERY few exceptions to the more-or-less universal firing order for in-line 8 cylinder motors of 1-6-2-5-8-3-7-4"
https://www.packardclub.org/forum/viewtopic.php?t=99&start=10

and this says the Chrysler is the mentioned "almost universal" 1-6-2-5-8-3-7-4
https://forums.aaca.org/topic/84374-straight-eight-firing-order/

so I'd agree with John, but it appears that MOST are the 1-6-2-5-8-3-7-4.

And here is a discussion that really goes far afield, but should answer some of the how and why questions...
https://forums.autosport.com/topic/35281-straight-eight/

So, looking at the crankshaft + camshaft (or checking compression if assembled) should give you the correct answer.

I remember memorizing firing orders many years ago for one job, and it proved the adage that for every rule, there is an exception. Almost all straight 4s (not flat 4s or V4s) are 1-3-4-2, except a small Toyota (1.2L?) which is 1-2-4-3.The wiki for that page also mentions "some older British engines".
This describes WHY firing orders are the way they are.
https://www.autoshackghana.com/firing-orders-of-4-stroke-internal-combustion-engines/

and the trivia for the firing orders (some guys just didn't get it, so we repeated it too much and I got bored) is that the Jaguar V12 is numbered A 1-6 bank and B 1-6 bank. I used to have that one memorized too. I never bothered with the VW W8 and Bugatti W16 since they are not distributor cap fired.