Just took the supercharger off of my 340. Was 8.5:1 compression. I asked the same question as you did, buy crate or have machine shop build it. In the end some of the FABO members talked me out of buying a crate engine as they are generally mass produced and you really don't know what is in the engine. I decided to go with normally aspirated 416 with 11:1 compression and Edelbrock aluminum heads. Good luck with your build.
