I've got a pretty stout 350 (around 400-425 horse) that got around 13mpg in a 93 extended cab silverado with 3.08 gears. I was going to put it in my 78 camaro but I'm going to wait until I'm done with the rest of it. I have a 84 olds delta 88 2 door with a 307. Will the 350 bolt right in. Any guesses as to what type of fuel mileage I might get. If I can bolt it right in will I still be able to use the exhaust from the 307 or no.