Volvo Penta AQ115A/100B Advice Needed

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I have an AQ115A engine which i'm getting work done on but may be in need of a new outdrive if i'm unable to source parts with the model being so old. Does anyone know of an outdrive model which would be most compatible or the most straightforward replacement for this? I know i'm not going to find anything that just fits perfectly into place without it being another 100B but any advice/guidance would be really appreciated! Thank you