Cadillac CTS First Generation Forum - 2003 - 2007 Discussion, 4.3L Swap??? in Cadillac CTS Coupe, Sport Sedan and Sport Wagon Forums; the gen 5 eaton on the l32 is a little better than a port and polished gen 3 you would ...
The HFV6 replaced the 3800. Even supercharged, even with the better supercharger, the L32 made/makes the same horsepower as the base LY7, (+/-) 260. Yes, it can be made to make more power... pretty easily at that. Smaller pulley, bigger injectors. But for the price of dropping that into a CTS, you could make the V6 that is already there way more powerful.
The 4.3 will at least fit in the engine bay of a CTS without any trouble, or should. Even though its bigger in displacement, a pushrod engine is generally going to be noticeably smaller than just about any DOHC engine with the same number of cylinders.
The straight six Atlas probably wouldnt fit. Or at least I seriously doubt it would fit without moving the radiator to the back. But a dry-sump, F/I Atlas, with a rear mounted radiator would be amazing. Maybe ditch the spare tire and mount the radiator there. But that is a super neat engine. I think it should be everyone's direct replacement for the 4.0L inline six engines in their Jeeps. There are not nearly enough forced induction I-6 Atlas engines either.
If you are going to drop a inline six into a CTS, make it a 2JZ-GTE. Some of you GM geeks might hate me for that, but as far as inline sixes go, there is not a better engine than the 2JZ (unless we double the displacement and go 5.9L Cummings!!!)... Hell, put a 4BT four liter Cummings in a CTS.
Never thought I would see a v6 power war, personally I would go with the v8 not only for power since some v6s can been tuned up, but for exhaust sound, I miss my v8 growl but other than that I like saving gas.