....Resin isn't going to be rubbery. To get the rubber texture , you will have to coat the resin cast steering wheel with a rubber grip material....like when you drip the handle of a hand tool to give it better grip. Anything that would be rubbery upon being poured/cured would end up being too flexible.
Alumilite does have a line of Flex resin and a line of Foam series, but that being said I don't think either one will give you the proper strength a steering wheel needs - you'll need to use a regular "hard" resin like RC-3 and coat it like Brian said. The coating is where the Flex and Foam series would come in. I know the Flex can be poured on but I'd create a mold, cast a hard resin wheel smaller than needed and suspend it in the Flex (either by pouring a thin layer and letting it harden up first) then pouring the Flex over the hard wheel to create the flexible "cover".
Alumilite does have a line of foams and of plastics, one of those might be what you need - look under the link for the Casting Resins. I haven't used either the foam line or the plastic line so I'm not sure which would be best but that's a place to start at least.