A friend has a '59 Plymouth Fury with the original 361 B engine and pushbutton transmission. It is badly sludged up and now won't start at all (tentative diagnosis is a jumped timing chain, pending further evaluation). This was complicated by a previous "mechanic" messing up the firing order (cyls. #2 and #4 were swapped) and hooking up an electric choke to the coil positive... an Edelbrock carb too... I'm amazed that it used to run at all.

Anyhow, he's interested in swapping in a later B like a 383/400 so the car is driveable while he has the 361 rebuilt. Will any B engine through 1978 be a bolt-in without problems with the torque converter, bellhousing, starter, balance, ? I don't know much about the engines before '67 so any hints appreciated. Thanks.

The early, pre 1961 Mopar V8 of all sizes had a lot longer crankshaft distance and bolt pattern to the rear crankshaft flanges from the rear main bearings, 8 bolt hole with studs in the flywheel or converters and no converter and flywheel centering ring on the backside of the crankshafts to locate the converter or flywheel.
The early converters and flywheel slip over the outside of the crankshaft flanges and center off of them
Dang them engineers anyways ,

It's not a simple swap because as Cab said a later engine won't bolt to the original transmission because of the differences in the crank flange that changed to the newer style in 1962.

I'm not sure what kind of balance or other issues you'd run into, but you would need to run an early crank in the later engine. Or, find another '58-61 big block.

You could swap engine and transmission as a unit, but this is another can of worms because of mount differences, the parking brake on the back of the original trans, push button shifter cable etc.

361

This is where there are 2 paths: restoration/original or updated...

The '59 will have the old brakes, e-brake/parking brake, ball & trunnion ft U-joint, and tapered axles.
A later complete drivetrain is more easily serviceable, both parts & maintenance.
Rearend width & probably saddles, AT shift mechanism, and e-brake cables would have to be figured out.
IIRC, changing the rooster comb in a later Torqueflite to the '65 part solves the push-button issue.

If it's a restoration, while the engine's out, there's plenty of time to work on other areas.

The complexity of the swap makes a temporary swap impractical. Either lay the car up during the 361 rebuild or update the entire drive train as topside advised. A 727 from a '62 full-sized car solves the parking brake issue and the '62 shift cable will hook right up to the earlier PB shift mechanism.