the engine itself will fit, but pretty much nothing else will. gearbox could be used but you may have to swap the driveshafts for later MK1 cab/scirocco items depending on the age of your car. exhaust manifold you need to either get a conversion 4 branch, or make a custom downpipe. managment wise the ign controller off the 16v will swap over easily, ideally you want the isv control unit but it'll run without.
the above assumes you have started with a 1.6-1.8 MK1 with a 5 speed gearbox, if its an auto you need the steering rack, pedal box and linkage, if its a smallblock then you need the rack & linkage, and also have to chop the gearbox mouint off the chassis leg and reweld it further up. Also the MK1 mounts are different, you need big block engine and manual 5 speed gearbox mounts.
Then there is fuel system, if its not a GTI you need new lines and a pump, plus either a GTI tank or a late cab/scirocco injection lift pump. If its a GTI you can get away with benmding the fuel lines, but they may be knackered at the back so check them over carefully. Crazyquiff does a 16v conversion pipe set off the shelf, which come precut to the right lengths for a 16v kr swap.
