Max:
Check out:
http://www.geocities.com/clarkblumberg/911-912page9.html for some good information.
I've done two of these conversions. The first was a 67S basket-case that we just wanted to get rolling to see how the gearbox/steering, etc. was before a full restoration.
The second is a mildly built dual-port in my current 912 driver. Why? The car was so original that the numbers-matching motor was still in excellent shape and the case had never been split. Since I drive the car daily, it made sense to use a late Type I motor. The benefits are:
1.You can do the conversion without ruining or cutting anything.
2. Some of the benefits are an
inexpensive alternator (goodbye antique generator
direct bolt-in - everything can be reversed in the future; with dual carbs it pretty much looks the same and sounds the same.
3. I've always been a fan of the Porsche 4-banger, but we all know that development of that motor effectively died in '69. Sure, there are some suppliers of hard parts and some racing stuff, but it's pricey for what it gets you. On the other hand, the Type I motor gave birth to an entire aftermarket industry. You can pretty much duplicate the performance characteristics of the Porsche motor with a Type I for a fraction of the price. New, improved cases and heads are cast by aftermarket mfgrs. and any piece you could want is available either stock or heavy-duty/race.
The down side is this: There are numerous companies that manufacture and market sub-standard quality parts, so if you're building a motor, you have to be careful. Also, engine builders vary from legitimate, quality performance builders to "VW" experts who are really kids putting motors together in their back yard (literally) on the lawn.
Anyway, buy/build a T1 with maybe 80-90 hp and enjoy it. You can use it as a reliable daily driver and you won't have to lose sleep if you happen to over-rev it.
Bill.