Big block will be more fun if you have the money to swing it, not only for the build but then to gas mileage which will be pretty horrendous if you like to get friendly with the loud pedal. :lol:
They don't weigh THAT much more than a small block, I've never put them on a scale but an all iron SBC is supposed to weigh in around 575 pounds, and an all iron BBC should weigh in under 700 lbs 685 is what I read. Relocate the battery to the back, get a fiberglass hood, aluminum intake, aluminum water pump, and use headers instead of manifolds... I wouldn't be surprised if you didn't even have to put big block springs in it. With the battery relocated, and some lighter than stock parts I doubt if overall there would be 75 lbs more weight on the front than stock.