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Colin;
That's the classic symptom of worn valve guides, but NOT necessarily rings!! Oil is sucked down past guides and burned, during maximum manifold vacuum created when you released throttle at speed.
You don't state year and engine...
...if its an early 1800/B18 with the (not very effective) "umbrella" style "valve seals", which if you haven't touched them in a long time are likely hardened and quite often missing altogether, cracked and laying around in pieces under the valve cover (looking like something important has broken...there was a post about that once!), you might just try replacing them (easy!, just remove valve cover, remove broken pieces laying around, and remaining old ones, and pop new (flexible) ones from an upper end gasket kit back on). Try this first...it's easy and inexpensive, and may help symptoms a bit...if not, head rebuild time (see below)!
...if it's a late 1800/B20, it will have the much more effective, (real) valve seals located right on top of the guides...if you have that style seal, and they are in OK shape, and are burning oil through the guides, then it's most likely head rebuild time too!
Head rebuilding notes in addition to the usual stuff:
Don't allow shop to shave anything from head if it checks out as straight on surface plate...this would raise CR and could lead to pinging, otherwise allow them to remove absolute minimum ONLY!
Install hardened seats so that you can put all concerns of valve seat recession and being compatible with no lead fuels behind you.
Also, dont be so quick about replacing those worn valve guides! I saw first hand, a teardown, after 100kM of strictly knurled and honed guides, and they were still nice and snug, perfectly servicable... moreso than after the original first 100kM when they were solid! I was really impressed once again by the o.e. materials used! Consider this low cost solution!
Cheers, and Happy Birthday America!
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