I will start by saying this will be long so if that is a problem quit now. This whole story started with me looking for a set of 1 ton axles for my 1/2 ton about 3 years ago. I stumbled onto a complete K30 for $900 and decided that instead of parting it out to build it into my rock crawling truck. Recently the 454 was converted to lpg for two reasons. A) it will run upside down and B) it is about a 1.25 a gallon cheaper than gasoline. I have been doing the conversions to LPG on modern trucks on the side for a local LPG distributor for a long time and when reading some old impco manuals I noticed that it showed what was required to make the system work as a blow though setup in a supercharged application. Even before I had started to collect all the pieces for the propane swap I was planning on turbocharging the truck. Just for reference before we get into the base line numbers on gas and lpg I will list a few specs. The 454 is an 80K mile Marshal engine rebuild L19 (peanut port, 7.8 to one compression). The only modifications to the engine are; Weiand Street Warrior peanut port intake, 204/214 .495/.510 114lc cam and headers. The drivetrain is a sm465, 205 and a 60/14 with 4.11s. The base line numbers after spending a few hours correcting the a/f curve on the factory q jet where 238 hp and 338 ft/lbs of torque at the wheels. Using a 70% correction factor for losses in 3rd gear and through the transfer case I get approx 340hp and 482lbs of torque. I rebase lined the truck on lpg. The carb/vaporizor is an impco 425 and a model E. The new wheel numbers were 206hp and 302ftlbs of torque. With the same corrections factor we get approx 294hp and 431ftlbs. I knew there was a loss with lpg, but wow. The power curves were identical but lower for lpg. After running a few tanks to be sure the lpg was working well, I started on the 3 phase of this truck engine build up. I purchased a used SC6176 precision turbo from my buddies that own a performance shop. I also bought a Tial 60 mm wastegate, 2 VW blow off valves, a crap load of 2.5" mandrel bent Us, a T4 flange, various 3.5" elbows and a boost controller. I also purchased a set of street rod headers. At the very beginning of the build I discovered the street rod headers wouldn't fit in the conventional manner, so back to the drawing board. I decided the easiest thing to use was factory manifolds. Fitting them 180 deg from there typical mounting proved to be the easiest way to run the hot side piping. The only problem with this is if you flip BBC manifolds the ports no longer line up requiring me to move the mounting holes .300". Though it is a little Hillbilly with a mill I was able to machine the bolt holes to allow the ports to match. So other than that it was pretty straight forward. I decided that over the driver fender would be the best turbo mounting and the exit pipe would fit in between the inner fender and frame running the exhaust down the outside of the frame.
This is a crappy youtube vid.
http://www.youtube.com/watch?v=z8I80HK3b_g
Just cause I am kinda a prick, I will leave you hanging on what the actual numbers it put down were. Still a bit a tuning to do anyway. If you wonder why I need so much hp my only answer is cause I am a dumb farmboy. I like power and getting 2nds and 3rds at the street stock truck pulls wasn't enough.
Your guesses are welcome and you can release the trolls.
This is a crappy youtube vid.
http://www.youtube.com/watch?v=z8I80HK3b_g
Just cause I am kinda a prick, I will leave you hanging on what the actual numbers it put down were. Still a bit a tuning to do anyway. If you wonder why I need so much hp my only answer is cause I am a dumb farmboy. I like power and getting 2nds and 3rds at the street stock truck pulls wasn't enough.
Your guesses are welcome and you can release the trolls.
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......from the looks of the twist on the dyno it's running pretty good 
