Well first lets start with facts about the two motors in stock form. LS1 is less efficient, it makes less brake horse power per liter than the 4.6L 4V motor. I have posted these numbes before but i’ll do it again for discussion sake.
Stock F-Body LS1’s are quoted to make between 305-325 HP depending upon model.
So lets give them the benifit and say 330HP, divided by 5.7 (liters) = 57.89 BHPL.
Stock Corvette LS1’s are quoted between 345-350 HP depending upon year. 350 divided by 5.7 = 61.4… LS6 in the Z06, 385/405 HP depending upon year. 405 divided by 5.7 = 71.05 BHPL.
Now those aren’t bad numbers. But lets review the 4.6 4V
2003 MACH 1. Quoted to make 305HP, now we all know thats off a bit, but for argument sake, 305 divided by 4.6 = 66.30 BHPL. Now the 01 SVT COBRA was quoted at 320, and we know the MACH 1 actually makes closer to 330 HP, so lets say its 330 BHP. 330/4.6=71.7BHPL.
Ok, well now we know for certain the 4.6L is more effiecient at making power than even the mighty LS6 or at least **** close to it. LS2 is not any better either. 400BHP/6.0L= 66.6 BHPL.
Now you made the comment that an LS1 is cheaper to buy components for…well that may or may not be a blanket truth. Regardless, the LS1 will need much more prep work to hold the same HP. Fewer OEM parts can be retained for the upgrade in HP, they simply won’t support it. The 96-98 COBRA motor is an affordable and a superior canvas to start with. The block can hold 1000 HP with only minor prep. The crank needs little to no work to support 1000 HP and the heads and intakes need only to be ported. The valve train needs to be updgraded, but for the most part more OEM parts can be used/retained saving you money. The LS1 to make 1000HP will need a freaking laundry list of new parts. Hell, to even make 600RWHP you need a bucket of $$$ for the LS1. The 4.6L 4V you just slap a blower onto a block or your choice be it AL or Iron, make sure you have forged pistons and rods and your set to jet.
better motor man.