a sort of easy way to think about 35mm lens equiv's in 4x5 format is take he focal length
and multiply it by 3 and you will get around the same thing in 4x5 ... ( for ex, a 50mm on a 35mm is around a 150mm on a 4x5 ).
if you are used to using longer lenses try longer tele-design lenses like the 10" tele raptar, sometimes mounted in an alphax shutter.
don't forget if you use your current lens for close-work you might need to add extra light / time to compensate for bellows extension
have fun !