What calibre as that makes a difference to what glass to put on?
Sportmatch had pretty much taken over the mount market by 1989, though an Apel HW would always be nicer.
Scope wise then I think Tasco were still making nice glass. .177 then a 4-16 x40 AO; .22 then any 3-9x40AO. Some Nikko Sterlings weren't that bad then. The tricky bit is to find something thats quite good and not all marked up. Heck an old Leupold would be very nice.

Many would say keep it as it is even though its pretty factory looking with all the Venom work in the innards. Being a Venom custom then the rifle can be reblued. Upgrading the stock even. But that investment really depends on how well it still shoots first. Nat driving fantastic then invest however much you want. Or just enjoy it for what it is; nice catch.