In New Zealand, 55-57 Ford Mainlines and Customlines came with autos or awful 3-on-the-tree manuals. We used to soak up imported Aussie assembled Canadian Fords by the boat load if your folks had off-shore funds. The second option was the English Zephyr Six which had a raunchy in-line six which loved headers and triple carbs, and often got fitted with four-speed boxes from 1966-1970 V6 Fords. This was the "Dagenham Dustbin"4-spd trans you have. The engine produced around 125-140 hp net, and 170 lb-ft in a 3000+ pound car.
In Kiwiland, the then common 272/292/312 Y-block had a spline count the same as the Zephyr 4-speed transmission used in the English V6 2.5/3.0 Ford Zephyrs/Zodiacs. So many back-yard hot-rodders used the trans in droves. They were nowhere near as stong as the 3/4-speed Toploaders of the post 68 era, but are OK if lubricated and not abused. Try ATF and look after it.
The US 2600 cc Capris used a puny fourspeed Hummer trans which was similar, but its not a good replacement. The best optin is upgrading, so plan to go T5 or Toploader, but don't get a complex about it. A Y-block didn't take the trans appart, your six shouldn't either. But any trans 37 years old is gonna need some work, so don't spend a sheckle on it apart from keeping it well oiled!