I have just bought a golf gti 20v 1998 mk4 and found that someone has patched up the engine and its got a cracked block that has now begun to leek so what i would like to know is......

1 Does anyone know if all 1.8 engine blocks are the same on the mk 4'S
i.e i have an AGN engine code according to the elring head gasket catalogue AGN ADR APT ARG and BAF engine codes all use the same head gasket can i use a block from any of the above to replace my cracked lump
all the above engines are 125BHP but i asume they probably all have different cams to alter torque curve and fuel economy etc possibly compression ????

2 Are the blocks wet liner and can i remove the liners and replace with my own if i can find a cheap block cause say a piston has seazed or something or a bearing has run on the crank and i can just swap my bits in to a second hand block?

3 i know where there is a 20v passat engine but its a 96 are these the same engine block.

Any help would be appreciated im not so up on mk4's as im a classic dub fan if i got a compleate angine from a passat say ann ADR engine code are the engine internals all the same or have they got different pistons to alter compression or is the bottom end just the same and i might have to just swap the cams to bring it to AGN spec