Could be, but Volvo was pretty performance minded on the P1800, and the 130BHP or so of some models is probably too much for a D type. I'd expect another OD model.
Look at the stamping plate on the OD unit.
If it says its a D type, and has a model number that starts with a 25, then its suitible as a starting point for a transplant.
Dont forget that this isnt a pain free drop in. You still have to shorten your driveline, and weld on the appropriate flange coupling.
Oh, and if it isnt already obvious, you need a Sunbeam OD tranny with matching adapter.
Jarrid Gross