I agree with Doug, all the early Olympus cameras came with the same range of focusing screens (the "1-series" focusing screens) and though these are not as brigt as the later (rare, fitted only to OM-3Ti and OM-4Ti) 2-series screens, with a 50/1.4 you should have a very bright viewfinder.
Note, however, that the OM-2 viewfinder is dimmer than the OM-1, because the OM-1 has a solid mirror, whereas the OM-2 has a semi-transparent mirror to feed the TTL OTF metering system behind the mirror.
So, I believe it is true that an OM-2 with a 1-series screen may have a dimmer (though much, much larger) finder than, say, a modern DSLR with a 50/1.4, but it should still be pretty great. And no modern DSLR can come close to comparing with an OM-1 viewfinder.
What I suggest, though, is to get yourself a new (standard 1-series Olympus) replacement focus screen, I've bough old OM bodies with terribly dirty/hazy focusing screens. They are regularly available on eBay. The 1-8 all-matte screen is nice and bright, and fine-grained.
I suggest that only once you've put in a new clean focus screen, and you are still unhappy, to look at other possible remedies - a third-party focus screen (usually expensive), looking if your pentaprism has started to loase some of its silver coating, etc.
P.S. You seemed to have received a great deal, enjoy a fabulous camera!