hello ! I have a Volvo 340 with intentions of putting a Volvo 440 1.7 turbo engine into it what gear box and diff would/could I use ? HELP

Standard gearbox and diff, if it's for drifting then weld the diff.

Just make sure you have good engine mounts and the propshaft is aligned or you will snap the propshaft.

Should fit right on the 340 clutch housing but I think you need a pilot bearing.

How do you, in fact, check the prop alignment?

Rent the laser alignment tool from Dai