I think you have to be practical when looking for 'equivalent' lenses in 8x10. Mainly because there are fewer focal lengths available for 8x10, and some of those are much rarer than others and therefore may be hard to find. Personally I would just get a 240 or a 300 based on the best deal I could get and what was available. If you get too picky you could wait a long time for the right lens at the right price.