I'm thinking w/a 307 SBC in a 4000 lb. car, pulling another 4000 lbs-plus of car and trailer, a big cam isn't what would be usually called for. A small, short-duration "torque" or "RV"-type cam is what will usually work for towing, then an aftermarket head might serve no useful purpose. Unless the aftermarket head was carefully chosen, it could actually hurt the engine's ability to make as much torque down low as possible because of the valves and ports being too large.
That said, another option would be to go ahead and cam up the 307, add some mild aftermarket heads, and then gear it w/4.56's. Add a 700R4 (or an OD stick tranny) for the OD to bring the final drive ratio back in the area where the engine won't be buzzing on the freeway (ratio would be 3.2:1 in OD with a 4.56:1 rear gear).
But this will require the engine to be spun up good to make its power, obviously. The easiest way to cure all the probs would be a bigger engine to begin with, IMO.
But for a budget deal, I would still opt for the 416's w/stock valves along w/a good 3-angle valve job and headers, over the PP heads and 1.94" valves.