With enough time and money, you can do almost anything. From a practical standpoint, I'd be concerned about passing your local emissions tests if you "downgrade" the engine from FI to carbs. In the US, '85 was the first year for the B230F engine in the 240 (except for the '85 B21FT turbo engine -- but '85 was the last year for the 240 turbo option).

From a mechanical standpoint, you can drop any of the B21/23/230 engines in and they'll bolt up. But you'll have a rather detailed and tedious chore matching up the required electrical, electronic, and fuel subsystems to the chassis systems.

With a bit of care and preventive maintenance, the FI system should work very well and very reliably. Why not stick with it?
--
Don Foster (near Cape Cod, MA)