This! Deciding on the best cam for you is 1/2 interview and 1/2 what it takes to go down track the quickest. If you want to take a look at some of the methodology behind the Summit Pro LS cams, here's a link to an article we did on the subject. We will have another announcement later this week on the subject.

 

I would definitely decide now if I wanted a boosted set up. Building the best NA set up means 11.3 to 12 to 1 compression for 93 octane pump gas and will be getting into too much compression boosted unless you want to go E85 or change to lower compression cylinder heads. Also build a good NA 383 LS1 stroker means 4 inch crank and the piston will have to be selected accordingly. That type of piston isn't as well suited to boosted applications because the area for the tingling tends to be more compact. I have a 383 LS1 stroker I'm speaking from experience on how we built it.

I've never done a turbo or supercharger set up so I don't know exactly the cost or what's involved. Junk yard 5.3 with turbo sounds like the hot set up these days. I'm a daily driver type and road trip my stuff 1300+ miles so I've stayed NA with all of my builds and cars.

FWIW - a 4 th Gen M6 with good heads and cam LS1 with 4.10 gears is alloy of fun with out being a budget buster. Making ~430 to 450 is pretty budget friendly if the motor is in good shape. I know three people plus my self that have LS engines with 250,000 to 300,000 miles on them that are running great. Another torn down a 297,000 mile 4.8 for a turbo build that still had factory cross hatchin in the bore. He said he'd have just ran it if he'd have know that

Spray can add a lot of power for the price. I've not used it but had my 383 LS1 built to take a 200 shot in case I want to one day.

Honestly, deciding on a budget of how much money you are willing to spend. Doing a 383 LS1 stroker short block from say will cost ~$3900. With your goals in mind the Scoggin Dickey Performance Center 427 LS short block with 24x crank for ~$5,200 are good affordable starting points.
SDPC LS. 383 Aluminum block
Scoggin Dickey 427 LS

A quality top end package heads , cam intake can easily hit $4,500

​​​​​​So for that 383 LS stroker I would be planning $9,000+ for the 427 say $10,000 +

Fuel system - will need upgrade $300 to $700
Transmission - probably need at least a new clutch set up $800 to $1500 easily
rear end - at least a Hawk's 8.8 or MWC 9 inch, plan $3200 to $5000

headers, y pipe or x pipe dual - plan on $1000 to $3000 depending on what you want
Other suspension stuff torque arm, rlca, panahard etc $800 to $1000

Don't forget tires & Rims $500 to $5000+ depends on what you want

Install & tune

FWIW - in my ~3200 pound RS Camaro when 465 whp 442 wtq 383 LS1 is fun to drive, has good street manners. The TA with 517 whp & 471 wtq (way more low end torque ) is fun too but it's much harder to hook up the power on the street. From a hard roll both are fun but the RS my choice because it hooks better. With a few tweaks that compromise drive ability either car could gain another 25 whp to 50whp.

You might want more than that...a lot of folks do.

 

For a M6 street car, you can't go wrong with a BTR stage 2 or a Cam Motion Titan 4.