You'll have to test fit it, probably multiple times to decide if it needs more clearance. Same for the shifter, you may need an aftermarket shifter if you can't make it fit. If you call it "clearancing" instead of sledge hammering it'll sound more professional and it'll still work the same. I used a C4, mostly because I had one, and had to tweak the firewall a little. My truck had allegedly been someone's drag truck with a 302 and C4 before I got it. There is no way that thing ever passed tech at New England Dragway as hacked up as it was.