On a nostalgic note: It is always sad to remove the original engine off an E3. The E3 is a light and agile car with perfectly matched engines. Nothing beats the happy revving of the 2500/2800, the almost linear power of the 3.0 S or the bite of the 3.0 Si, regardless of Zenith or D-Jetronic. Later engines have more power for sure, however, that does not compensate for them feeling heavy.
The pragmatics: The earlier 3.5 has 93.4 mm x 84 mm bore x stroke = 3453 cc. The later has 92 mm x 86 mm = 3430 cc. Two different characters. The early engine is more aggressive but also more prone to heat cracks. The younger one is a well-behaved tourer and reliable from here to eternity as long as the piston rod bearings are replaced every 200000 kms and the oil pump works. Always warming up and cooling down the engine goes without saying.
The Chevrolet: This may work in America, I hardly know anything about it. In Germany there are rumours when GM still owned Opel they put a small block in an Opel Omega to compete against the BMW 5 Series and others. The project is said to have been abandoned at trial stage as the Chevrolet engine was found " unsuitable for the Autobahn".
The pragmatics: The earlier 3.5 has 93.4 mm x 84 mm bore x stroke = 3453 cc. The later has 92 mm x 86 mm = 3430 cc. Two different characters. The early engine is more aggressive but also more prone to heat cracks. The younger one is a well-behaved tourer and reliable from here to eternity as long as the piston rod bearings are replaced every 200000 kms and the oil pump works. Always warming up and cooling down the engine goes without saying.
The Chevrolet: This may work in America, I hardly know anything about it. In Germany there are rumours when GM still owned Opel they put a small block in an Opel Omega to compete against the BMW 5 Series and others. The project is said to have been abandoned at trial stage as the Chevrolet engine was found " unsuitable for the Autobahn".