If it's D-jet it must be a 73, in which case many but not all of the FI parts will fit an 1800E. 74 is K-jet (aka CIS) which has the same manifold casting but everything else is completely different.

A quick way to tell the year---73 has vent windows in the front doors, 74 does not. 73 has medium size bumpers, 74 has huge ones similar to those on an early 240.

If it's a 142, the doors are worth keeping if they are straight and not badly rusted.

If it's a 74, note that there were some quality control problems in this year: The bodies were made with some components of Russian steel, and the rustproofing was inadequate on Belgian assembled cars, both of which can lead to horrendous rust problems. This was also the first year for the "metric" B20 (a transitional type made at the new Torslanda engine plant) and they often were not up to par. Block castings are sometime porous, and prone to rapid cylinder wear, and I've seen a couple where the block had actually warped. The cams on this year also tend to wear rapidly. However, the head is a good one, with hardened seats installed at the factory, and the gearbox is too, with a reinforced case and larger diameter bearings on the idler shaft.