Based solely on how long each of those engines has been out of regular production in a vehicle you will find it a little easier to get parts and speed equip for the 292. There is still a lot around for the 302 Jimmy once you start digging but new versus used and prices might still make the 292 a more attractive base to build from. As Bald Eagle says the 302 also has a weight gain over the 292, something else to consider. You can still buy parts from Chevy for the 292 and can in fact buy a complete engine from them. Not so with the 302.
Personally I would choose the 292 and if I had the extra 100 bucks I'd snatch up the Jimmy as well. If you can't use it someone else might.
Mike
