For 1970, the mid-sized Buicks once again received new sheet metal and the Buick Skylark name was moved down another notch, replacing the previous Buick Special. The Skylark became the entry-level Buick available in two- and four-door sedans with the 250-cubic-inch inline-6 as standard and the 350 cubic inch V8 (260 horsepower at 4600 rpm) available as an option.
Replacing the previous Buick Skylark was the Buick Skylark 350, available as a two-door hardtop coupe or four-door sedan with the 350 cubic inch V8 as standard equipment. This 350 cubic inch engine was a different design than the Chevy's 350 CID engine (4.000 in × 3.48 in) the Buick design had a longer stroke and smaller bore (3.80 X 3.85 in) allowing for lower-end torque, deep skirt block construction, higher nickel-content cast iron, 3.0 in (76 mm) crank main journals, and 6.5 in (165 mm) connecting rods, the distributor was located in front of the engine (typical of Buick), the oil pump was external and mounted in the front of the engine, the rocker arm assembly had all rocker arms mounted on a single rod and were not adjustable. The Skylark Custom continued to be available, also using the 350 cubic inch V8 as standard equipment and still available as a two-door convertible coupe, two-door hardtop coupe, four-door hardtop sedan, and four-door sedan. Buick Gran Sport models continued to be available as a separate series. The Buick Sport Wagon name was now used on a conventional four-door station wagon that no longer featured a raised roof with glass panels over the cargo area, or a longer wheelbase, as in the past. It now used the same 116 in (2,946 mm) wheelbase as the Buick Skylark four-door sedan and the now-discontinued Buick Special four-door Station Wagon. It became, in effect, a Buick Skylark four-door station wagon in all respects but the name.
There was a GM VIN# error on one 1970 Skylark. This car ended up with a GS455 stage1 engine, suspension, transmission, and brakes, but it has the regular skylark 350 body that has GS badges. This case has been verified from GM and is documented.
Source: Wikipedia, 2012