The 390 CFM Holley 4-BBL carb will add plenty of airflow without dealing with all the headaches of multiple carbs. I seem to remember that there's a bigger intake valve available, but I can't recall what engine it comes from. If you open up the port under the valve and blend it in right, the breathing with the bigger carb will be improved considerably. A modest increase in cam timing and lift will also help, but don't go ovdrboard on duration. A relatively short duration, high lift cam is what builds torque for trailer towing, so try to get someone to grind an "RV-cam" profile onto a 235/261 hydraulic cam core if possible. I wouldn't go over 260 degrees duration, but get as much lift as your cam grinder can supply. The 261 engine can handle an .080" overbore without getting into cooling system problems, but be sure and run a good radiator and plenty of fan if you go overbored. There's a thread somewhere on this site that describes an offset stroker modification on a 261 using a 292 Chevy connecting rod that will increase the displacement, also. I believe it's possible to get the cubes up to 280 or more with the right bore/stroke combinaation. With an 848 casting number cylinder head modified with the 261 head "steam holes", the compression you're looking for can be achieved with just displacement increases, I think. These types of modifications get pricey in a hurry, however.
Jerry

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