The 61 - 62 engine compartment is the same, 63 is the same width as the 64 - 66 but 64-66 is a bit longer from what I remember. I'm sure TTI's wont fit 61-63 cars but spitfires might work with a bit of work. Stock 273 manifolds do work with minimal grinding around the steering shaft. I used V8 mounts from a 64-66 car in a 62 Valiant with a 318 and 904. We pulled it from a about 71 Scamp. The mounts were used and once in a while we couldn't figure out why the steering would 'jam', later we realized when accelerating hard the motor would touch the steering shaft. The distibuter will sit up tight against the firewall so you'll have to tap it out a bit. I used 1/4 thick aluminum to raise the engine a bit to clear the center link as back when I did the swap I didn't know about the V8 later center link being a bit more drop for oil pan clearance. The other big thing is the heater box is in the way. I believe I also used a 90 degree oil filter adapter.
I did this swap a long time ago and that's about what I remember...