first generation Lumina shared the engine and transmission with a bunch of other non-W-body GM products. Beyond that, I think they only thing remotely related to another platform were the stereos and pieces of the rear suspension, namely the leafsprings, which seem to have borrowed their similar fully independent design from the Chevrolet Corvette, but this was also true of the other first gen W-body cars. As for the second generation Lumina (1995-2001), the only non-powertrain parts shared were the stereos. The rear suspension was specific to the Monte Carlo and Lumina, while the front was shared with other first generation W-body cars (1988-1996 Pontiac Grand Prix, Buick Regal, and Oldsmobile Cutlass Supreme). This has led to the 1995-1999 Monte Carlo and 1995-2001 Lumina W-body chassis being referred to as generation 1.5 of the W-body, as it's not completely generation 1 (with the lack of a rear leafspring), and generation 2 didn't debut til 1997 on the Pontiac Grand Prix, Buick Regal, and Buick Century.