I have a Subaru Impreza uk 2000 classic, had the standard version 5/6 turbo engine in it. I need a new one and was wondering what other engines would fit into this particular car?

Can do a 2.5 conversion if you really wanted to 

 

depends what you want it for

Something with v5/6 heads would be the easiest option (straight swap )

V1 to v4 are interchangeable as the inlet ports / stud pattern are the same (although the inlets look different )

.v5/v6 run a completely different phase 2 inlet manifold /fuel rail type which doesn't work with earlier or later inlets /head ports.

I think you can buy phase adapters to make most inlets "mechanically" fit different engines but it can sometimes lead to loom splicing due to having different sensor plugs .

So basically it's possible but using a engine with the same v5/v6 phase 2 heads would simplify things [emoji6]

If it's not broke .....upgrade it 😊