Is the chassis for Mk3 and Mk4 the same?
Did VW just change the outer body and keep what's underneath the same?
I have a 95 golf (Mk3) diesel, runs very good, but body is falling apart.
Still want a diesel, but all Mk4 diesels cost to much $. Gas Mk4 are in my $ range.
What I'm thinking of doing is getting a gas Mk4 and changing over my diesel engine into it.
No a mk4 is not like mk3 mk2.... Its more mk1
Also... No idea where you are...emissions for mk4 will be your biggest issue if inspected...
Engine mounts are very different on the Mk4 cars. They completely changed the engine designs with the Mk4 - trying to fit an earlier engine in to a Mk4 body will not be easy at all.
Also like CRSMP5 mentioned emissions will be a bit deal if you are in an area that checks. All the Mk4 cars are OBD-II while your '95 engine definitely is not. If you've got a '95 diesel I'm assuming it is an AAZ as well which is a cable throttle engine - all the Mk4 engines were drive by wire, so there is no factory accelerator cable available.
The later you go in to the Mk4 chassis the more the cars become dependent on CANBUS - this is basically an in-car networking system that allows all the various vehicle modules to communicate. The ECM is obviously a big part of that. If a factory ECM is not in place and functioning you will have issues with all sorts of other things.
Stick with a '99 or earlier Mk3 chassis - it will be much easier to bolt everything in.
I've seen a mk2 1.6na in a mk4 Jetta. No emissions tests so there was no issue there. It's a lot of work but if you don't mind a lot of things not working it could be worthwhile. You will need to know how to weld and make motor mounts though.
my vr6 mk1 rabbit has mk4 mounts installed in it. uses some custom bracketry on the motor and a custom dogbone mount but works like a charm.