Derry,
Take your existing radiator to a radiator shop that builds radiators for race cars. Mid-Am, Late Model, etc. Ask the local engine builder who they recommend. You will then be pointed in the right direction. You can then get a custom made radiator that will look right in the small engine bay and will keep the SBC cool. If you are just using it on the street, they can add a bottom tank cooler for the transmission. If you are planning on racing or towing, then do like Jock mentions and get a separate trans cooler.
If you are using an electric fan, the ONLY two manufacturers that I can personally recommend are SPAL and Tri-Pac. These are the only fans that actually moved the air at the published velocity and pressure based on testing. However if you will be towing, you will need more air flow than an electric fan can provide.
