1962.5, the mid year revision of the roofline and the apearance of the Futura/Comete and the Fairlane allowed Ford to pump up the firewall to fit the 160 teeth flywheel V8's. All were based on the same XK2000 'Falcon' tooling, and it was a cinch to incorporate the changes.
The Aussie 250's use the same early 160 teeth flywheel as the early 1965 to 1966 221/260/289 V8's ( still do today).
An Aussie 250 should just fit an early pre 62.5 trans tunnel. After 1966, the V8's went to a much larger type of bolt spacing, with small 157 and large 164 teeth flywheels, with two types of bellhousing. The block pattern on the US six bolt V8 bolt pattern 289/302/351's and US 250's and 240/300's make sledge hammer work mandatory, and the bigger Toploader, T5 and C4 type tranmissions require hammer work in the tunnel.
Same with the 60 and 61 Falcons and Rancheros...they need hammer time, and reversing of the drag link between the idler and pitman arm to clear the US 250 or 300 sump, but the Aussie 250 is quite a lot smaller than the US version.
If its late 62, it won't be a problem, but if its early 62, then you'll need to have a big friendly hammer. Best discussions were from 61 Ranchero...he shoved a 300 and four speed into his little black 1961 pick-up, and although it was hard work, it transformed a little underpowered truck into a seriously cool truck which looks totally stock on the outside. Powerband has a really good page on his postings. His Comete has a US 250, and it fits, but he had to swap over the drag link, and , from memory, smack the firewall with a hammer and gas axe to get it to fit easily.