Hey guys im new to this forum this is my first post and i need some help i am wanting to do a 12 valve swap into my 99 chevy tahoe i have the motor it is in my freightliner box truck im wondering how much power i can get out of it withought getting to much into the internals of the engine and which trans would be better the gm 4l80e or a dodge 47rh or whatever the dodge auto trans is what kinda mpg would i be looking close to with different hp setups tia guys
The 6bt i have is from a freightliner box truck it has the p7100 injector pump that has been turned up some already what all would i have to do to make 4-500 hp? I will post pics if i can find out how

 

This is some info on the engine itself