there are no under or over size inside diameter rubber seals for any of our SB or BB engines.

As Cab suggested, the early style rope seals would be your best bet. However, be aware that their installation is critical.. and.. the current material is very difficult to cut flush upon installation. The early original material was made with asbestos rope and graphite lubricated... easy to cut. The newer generation (for past 30-40 years) is now made with a Kevlar material and very difficult to cut... takes additional time.. and requires a very sharp serrated cutting blade... but the rope is dominantly replaced by rubber seals.

I'm a former gasket engineer and know the history of this matter.

NOTE: Certain late-model crankshafts can have a press-on metal sleeve installed, however, those designs of cranks cannot have a flange at the end. Similarly, many harmonic balancers have sleeve available to save the balancer and provide a new sealing surface.

Mopar Mitch "Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers! Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!