I was surprised this is NLA even in the aftermarket, but as a former B234F owner I was even more surprised to learn it was different from the other red block oil traps, yet it appears you're right. If it's built as solid as the other Genuine Volvo red block oil traps then I agree with others that there's a very, very good chance you can remove and clean it without breaking it. All you'll likely need is a new o-ring, which as I vaguely recall is the same as the distributor o-ring and commonly available. In the past I've had an aftermarket new oil trap standing by so that when I removed an old one and tried to clean it I would have a spare, but I've never had a problem. Once you've got it safely out of the block everything is downhill doing a bunch of flushing with something like paint solvent while you semi-carefully rod out some of the cake. You don't have to get everything, just enough to get it to breath properly for another 10 or 20 years. Good luck.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now