Seems to me a bigblock should be close to the same weight as an old stovebolt six,maybe a little heavier. I'm thinking it'd take some modifications but I remember seeing a gear-drive steering re-locator advertised in Rod-n-Custom recently. I'm looking for the ad now. Basically,you cut your steering column down at the firewall,you connect this box to the steering shaft,and it moves the end that goes to the steering box up,down,or to either side several inches for clearance.on the outside of the firewall you run a steering shaft to the steering box,connected with a couple of u-joints. That,combined with moving the steering box out a few inches should give you plenty of room for whatever exhaust you want to run.Another option might be the conversion to a Toyota steering box.There's kits for that one. Either way,you can run manual steering,one with the stock box,and the other with a newer box. I'm not sure but I think the Toyota box is a little quicker ratio. Lotsa options available to you.
Speed