i dont think there is a performance diff u jus cant put a keyed pulley on a non keyed shaft jus get u a quick change pulley kit from pulleyboys then u can swap pulleys real fast

 

I got a 2.9 on mine, with a press on quick change pulley kit. I run about 12lbs on my 4.8 with E85. Changing the snout from a press on to keyed shaft isn't necessary.

 

I bought my truck used, and it didn't come from the dealer with a supercharger. When I got it, I wanted a supercharger. I found one on eBay, and purchased it. It came with a 3.1, and a 2.9, and was a keyed snout. I ran the 2.9 for a while, and without meth I was pushing about 10psi. I ended up running a best of 12.49. My IAT's were quite high crossing the traps, and I wouldn't suggest going much smaller without meth, and the stock magnacharger cooling system. I have since went to a 2.6 pulley (It requires machining the snout), and turned on my water/meth. hopefully if things go right I can go to the track Sunday for the last day it is opened.

Don't forget that boost is actually a restriction of air entering the engine. So all of the stuff in my sig actually lowers boost. Heads, cam, headers, free flowing exhaust. That same pulley will make more boost on an engine with no mods.

 

I have a 3.3" pulley and see 8 psi on mine with mods in sig.. Keep in mind the smaller the pulley the more heat you will see on your IATs. I added an additional intercooler in series with the stock cooler for lower IATs.. Next mod might be a 90mm J-tube and an LS3 TB with an X-link. Having trouble finding a good tuner since zippy moved away so this is on hold.

 

Personally, I'd rather have a keyed pulley and shaft, than a press fit. For the same reason that I'd recommend pinning your crank pulley. At your stock & relatively low boost levels, it's not an issue at all. But since you are wanting to "turn it up"......

I'm sure BlownChevy would like to groove your shaft for you.