Thanks, Gerd. Insomnia is a wonderful thing.
Paul, since I'm on a roll here, keep another few things in mind. The bigger the numbers get for the engine, the more the rest of the car has to work to provide life-support to it. A larger engine will require more monitoring, a careful maintenance program and a decent annual budget for the rest of the car.
A car which started life as a Bug and was saved from salvage by becoming a kit car has all of the Bug's inherent weaknesses in it -- and the Bug was sawed in half to make the conversion work. These little guys potentially have a number of old VW parts in them, even if the car is described as being 100 percent new.
Not all of these critters are VW-based. Manufacturers nowadays use a variety of techniques, many of them using proprietary chassis designs. Some of them use very few original VW parts. It's important to know what you're getting, so I'd have a good read through the Makers tab (top row, fourth from left, above).
I don't know when the last VW shift coupler was made, for example. I know you can't order one from a Volkswagen dealer anymore, and there are a number of optional aftermarket ones available. The originals seem to last longer, and I personally would source one from a junkyard and clean it up rather than order a Chinese part of questionable lineage. Every car based on VeeDub pieces would be in need of the bushings that go into that coupler, too.
My point is, there are so many little subsets involved with making a car, or re-making a car, that your questions might want to address the little things as well as the big ones.
Did you know that it's possible to find a VW transaxle with something called an Automatic Stick? That thing doesn't fit into a stock Speedster without modifications, but I'll bet someone's tried it. There are a hundred different combinations of transaxles, spacers, axle tubes, axles, brakes and wheels, too. Most of the unaltered cars used to be produced with VW-standard, very narrow tires and stock Beetle wheels. Some people have really neat ideas on how to modify their cars to accomodate bigger wheels or meatier tires, too.
It's all good stuff and may require a little searching, but if you read enough and look at enough photos in the Photos section (above, middle tab), you'll be able to begin spotting the differences easily enough.
I wouldn't intend this for use as a guide, by any means, but I have several favorites here. Here are a couple I look at for inspiration:
https://www.speedsterowners.com/files/view.asp?sf=dubudee&f=topdwnnotonneautag3%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=lvillene&f=hardtop11%2EJPG
https://www.speedsterowners.com/files/view.asp?sf=drdemanto&f=hermosa05%2EJPG
https://www.speedsterowners.com/files/view.asp?sf=Johnny2bolts&f=Cabrio+Interior%5FJ%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=alanmerklin&f=1100%5F4964%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=landerso&f=DSC%5F0109%2EJPG
https://www.speedsterowners.com/files/view.asp?sf=Kawika55&f=DSCN2310%2EJPG
https://www.speedsterowners.com/files/view.asp?sf=MUSBJIM&f=OLDMAN%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=MUSBJIM&f=IMG%5F2748%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=MUSBJIM&f=Angela+Spyder%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=nichols1&f=Dash+View%2EJPG
https://www.speedsterowners.com/files/view.asp?sf=chines1&f=MVC%2D012S%2Ejpg
https://www.speedsterowners.com/files/view.asp?sf=mickey356&f=DSC%5F1554%2EJPG
and
https://www.speedsterowners.com/files/view.asp?sf=Jogyver&f=DSC05851%2EJPG
-- but I need to say that this isn't an all-inclusive list by any means. They're all different in one way or another. Some are different in a huge number of ways; every one of them has a story.
Good luck with your choices, but make them what you want, not just what someone tells you you need. :)