I guess so! I had a '63 Valiant wagon and put a 340/ 4spd from a wrecked Demon in it back in '75 and don't even remember having any firewall modifications. What I remember was having the 63 wagon and my 64 Barracuda sitting right next to one another and comparing while making the plan for the 340 swap. (especially the tunnel) Seems like a modification I'd remember, but then that was quite a few years ago!
