Complex sentence: It was originally based on the chassis design of the Morgan Plus 4 to which it combined the Rover alloy block 3.5 L, which had been purchased from GM-Buick in 1967.
Split into simpler sentences: It was originally based on the chassis design of the Morgan Plus 4. It combined the Plus 4 with the Rover alloy block 3.5 L, which had been purchased from GM-Buick in 1967.