B Engine question

[Aok]

Do any modifications need to be made to install a model B engine into a model A. I maybe be looking at one that has a 4 cyl B engine. I know it would have more hp and I think a actual oil pump so not too concerned about the engine just if changes had to be made to install. Like does it match up to the model A trans or is a adapter required and availability of B engine parts if needed.