Mopar "B" bodies don't have springs on the front suspension. They use torsion bars. If you're going from a small block to a big block then you'll probably want to swap them out for the heavier duty torsion bars. They'll handle the extra weight better. Out back you'll want to go with a set of super stock springs. Both the torsion bars and springs are available at Jegs. The springs go for about a hundred bucks and the torsion bars are around three hundred. You'll also want to make sure your differential has a pinion snubber. Mopar added those to big block performance cars to eliminate spring wrap.
"If money is what makes cars fast, mine otta be going 400 miles an hour!". - Felix Sabates