cracked gear case on 150xp trying to by compatible case

[jrmymllr]

Just took on a 89 ranger 350v restoration project it has a 150xp evinrude on the back with a cracked lower unit I'm shopping around for a empty used case and I'm trying to make sure I get the right one all of the model or serial numbers I see are six digits consisting of all numbers but I look up verification for my motor and its a 8-12 letter number combo will the parts I'm looking at work or not? If so how do i find my 6 diget number/code? Looking for some hellllllp