Hey there,
when converting from a B16 to a B18 engine there are a few differences:
B18 radiator is larger, won´t fit in the front middle section. With the B18 middle section the B18 hood is needed (different hinges). M30 transmission doesn´t fit on a B18 engine, M40 needed.

When converting from 6 Volts to 12 Volts take special care of the fuel gauge,
it´s the only electrical instrument which will give up on 12 Volts. You can either replace it with a 12 V together with the sensor in the tank or talk to some electronic geek for a voltage regulator to supply 6 V to your old instrument.

Replacing starter motor and light bulbs need no explanation I think.

Hope this is a little help.

Good luck,
Zig

I fixed up my '58 444 years ago using a '64 544 parts car. My impression is that the body and suspension parts will interchange between the B16 544 (1960) and the later (B18) ones that you have. I think the main exception is the hood, and front center section that support the hood. Those parts are different (B18 has different radiator and hood supports).

The rear axles on the B18 cars will have a different ratio.

Not sure when brakes changed (they had changed from my 1958 444). But if different, the newer ones will bolt on to the B16 backing plates. I suspect that the throttle linkage, clutch linkage changed with the B18. They were different on mine.

I found it pretty easy to use the B18 parts in the 444 and expect it will be even easier with the 544 if you are OK with destroying the "original" aspect of the 1960.

Hope some of this is right - a bit of a trip down memory lane for me.

Keith W.
1958 444
1989 740 Wagon

Difficult question to answer in a small space. Generally the "Sheet Metal" is the same. Engine, Transmission and remainder of the drive train will be different as Volvo moved to the B18 engine, M40 Transmission and the Spicer/Salisbury Rear end with the "C" model PV544 in 1961.

"Most" other components should be interchangeable.