502 firing order

[3500 Chevy 88-98 502]

Heya folks,

I have come across a 1993 chevy silverado 3500 with a swapped engine (502) I have little to no experience with cars. I've been looking at it with a mechanic who is considerably more experienced having worked on Cummins Diesels for a transport company. He's working on a truck of his own. I was trying to help him out by figuring out the firing order we've tried various ones, It doesn't appear to be misfiring but I have little experience with v8's so i'm not sure what a 502 or a 454 should sound like firing order-wise. I'd happily post a recording. Truck also has injection issues which means it needs a bit of help every time to start. It's also currently stuck in limp-mode as it will not exceed 1800rpm's. The computer has been 'tampered' with, presumably when the block was changed. It's currently with another mechanic who has a diagnostic system. 

Basically, I was hoping someone could post the firing order of a 502 and I could check when I get her back from the mechanic.

Thank you all in advance

[3500 Chevy 88-98 502]

Engine dates to somewhere between 93-96, it has 12k miles on the counter.

[Logan Lanfear]

1,8,4,3,6,5,7,2

Same as any big block I would wager.