If it's only going to the track occasionally, why is it you need 750hp for cruising??? Reason I ask, a 750 hp engine lugging around on the street in congested traffic is going to be a whole lot more problems then it's worth. Either engine is going to take in the neighborhood of $10K to build, probably a lot more and just isn't going to last in normal street use. Either engine built to that level of performance is going to be very maintenance intensive, and probably not live very long. 750 horse engines belong on the drag strip, and even then weekly inspections are in order to keep everything working good and staying together....

Even in a heavy boat like your Galaxie, a well built 390 with good heads is going to pull you around in traffic just fine.

Just thought maybe a reality check was in order, not meaning to burst your bubble.... If you can afford the $$$$$ for the build and don't mind working constantly to keep the thing running right, have a ball....