Here’s the thing: to do it right would take a big block stub frame, torsion bars, power disc brake conversion, correct steering column, heavier rear leaf springs, radiator, anti-sway bars and all the other miscellaneous brackets and do-dads. People who talk this big block swap stuff are blowing smoke.
Are the /6-V8 conversion brackets still available? If so, no need to swap a subframe.
If the car didn't have a swaybar, it's possible it got large-diameter torsion bars. My 68 Fury with 318 was that way. Would a /6 be the same? Only a measurement can say for sure.
Does it
need the disc brake conversion? IMO that's a good upgrade, but not immediately necessary, esp due to
@Triple Pickle having refurbished all the brake hydraulics. And at that point, IMO manual disks would be my preference anyway. I can attest - if someone can drive manual drums, they can drive manual discs.
Change the steering column? Maybe eventually, but drive it as 3-on-tree for awhile. Would need the bellhousing (as some folks have mentioned) but would also need the correct flywheel and clutch. And to shorten the Z-bar to V8 length.
Heavier leaf springs? I've been putting a 440 thru worn-but-leaf-added 318 springs (and a smaller-size rubber-insulated driveshaft) for years now.
Radiator is $250 upgrade to an aluminum one, similar to the replacement Pickle used.
The 'small' differential housing used behind smaller engines will last behind a 440 if it isn't abused. But with the 215-sized tires, they'll be a nice fuse for the driveline.
Are there expenses that most folks overlook? Absolutely.
But if wanting a 4-door to upgrade, this one is the best foundation a person is likely to find.
And IMO, the best change would be to a 5.2 Magnum, as it would provide a decent amount of spunk for a car this size and not require additional driveline beefing.
