You would have to change too much to be worthwhile. You could put in a Corvair engine the pancake 6 but you would be torching out the rear seats as the engine has to be mounted as a mid engine. Lots of work and has been done already. More show than go.
You bought a VW. They are inherently slow engines BECAUSE they are Long stroke engines. It is like a short person foot racing a long legged dude. The short persons legs is going to move faster than the tall guy.
That is the difference. One can move faster and the other one gets tripped up because he is gangly, or has less control of where his legs go so he has to go slower. Long stroke engines are found in diesel cars and farm tractors, they will have a lot of pulling power but instant take off "not so much" So you would have to change the crankshaft to a short throw crank and the piston pots would have to be shorter so that you get compression. So say invest $10,000 in the motor and you "MIGHT" have something faster. It is not a simple matter at all.
At the time I was looking at a RAJAY turbocharger as a cheaper solution...only $600 (in1972dollars) That was still pricey, and it became not that important. VW is not a race car. If I want a race car, I would have bought one. So I went fishing in the outback hills...which a VW can get to and your fast cars are stuck on city streets.
Swapping for another motor is basically out of the question. It is an abortion fitting.
Thing is, you may have bought a 1970 VW beetle (that got its motor swapped out for something smaller. Stock 1970 is 1600cc engine, and yet I have read where people got 1200cc engines in their 1970 bugs(which is the smallest engine you can get and that takes work to fit it whereas a 1300 would just bolt right in and mate up to the bellhousing no problem. But 1300's are in demand motors for dune buggies. 1200's are a weak engine and can't be modified at all. A 1300 can be upped to a 1500 just by changing the piston pots and pistons.
. To know what you got, really, you have to pull a head off and measure the diameter of the pot.
. Externally looking at them, all the engines look the same.
. I found a 1600 stock engine could lift the front wheels off the ground. Not quick, but torque it has. So it is expected to perform as a VW.
ANY WATERCOOLED ENGINE could beat it. VW is a bush buggy.
I would simply buy a faster car like a water cooled Honda. Less monkey business...and cheaper to get immediate results.
My other VW, I put in a V8 engine. That required A LOT OF WORK. So no longer a VW. More a Funny Car.