If it's still fuel injected, and you plan to leave it that way then you are going to have to rebuild it back to stock specs. Aircooled VW fuel injection is not adaptable to modifications. At best you could bump the cylinder size to 87's or 88's but it's not going to run very well if you go bigger, also because it can't compensate for major vacuum changes that are different from stock a cam or any head work(port and polish or larger valves) would also be out. But if where you live doesn't have the IM woes then there are lots of options.
First pull that old tired fuelie out of there (don't CUT anything... unplug it) and seal all openings and put it into storage as it will add to the value of your bug if you decide to sell it later. Make sure that you seal all the plug-ins for the fuel injection with electrical tape in the car then pull the high pressure fuel pump from under the fuel tank and plug and seal the return line both at the tank and at the frame horn in the back, and now would also be a good time to install a new fuel filter inline under the tank. From there it is a question of just how big is your bank account if you want to go fast. A used complete carb'ed 1600cc dual port engine in rebuildable condition is normally(in my neck of the woods) around $500.00 to $750.00 and this would give you everything you need to replace your fuelie. Another way if you don't want to purchase a used engine to rebuild would be to go ahead and tear down your fuelie engine and build it back up to what ever you want, just don't put the stock fuel injection system back on it. With the car set up this way you can run most any aftermarket setup or a stock dual port carb setup for that matter by just adding a electric fuel pump and pressure regulator(no the injection fuel pump won't work) Just remember to save the injection stuff as it will add valve to the car to keep it. The only other thing I can add is for starters, get a Bentleys offical VW service manual for your year of Bug it will be the best $40.00 you could ever spend. Next before you start draining that ol' bank account truly figure out just what you want and if you are going to do the work yourself or hire it out. If you hire out remember to add at least around 25 to 30 percent more to what ever you came up with for parts and machine work totals. Olspeed
66 Ghia, "Dexter" 76 flat window Beetle
It's not a Car it's a VolksWagon!