Originally Posted by bernie
Good point PigDog, specific to EL1XR8
IMO, the first thing you should get is a good exhaust system (headers and 2.25" twin or 3" single), cost $1500 - $2000 depending on header type, mild or stainless steel etc.
Not sure how much you know about superchargers but I have found the following sites useful.
This forum is for Mustang owners, but there is heaps of info relevant to supercharging the 5.0L
I recently purchased my Vortech (centrifugal s/c) kit from CAPA for $8000. This is designed for 10lb's boost on a stock engine. CAPA are claiming 300+fwkw with one of these kits and a good exhuast on a stock motor (there are some dyno graphs on the CAPA site). The kit contains basically everything you would need.
They also do a Powerdyne kit (also a centrifugal s/c) for about $6300. This is claimed at around 255fwkw. The Powerdyne install is also easier as it doesn't require a hole in the sump for an oil return line like the Vortech does.
I haven't fitted my kit yet so can't give you numbers. Officially my project is out of control (it originally started by just wanting to add a s/c to my 5.0L) as I also have all the stuff in my sig and more. I'm know expecting over 300rwkw.
Note the condition of your engine will also effect how well the s/c will perform. If your concerned a leak down test can help to establish the sealing performance of each of the cylinders.