You can go up to a 78mm crank and still have vw journals. As far as where to get a crank, I would recommend DPR or Demello. A nice welded, counterweighted, balanced, and nitrided crank should run you about $425-450. The strength of the welded crank really depends on the quality of the work done by the shop, and both Demello and DPR are known for the quality of their work. You shouldn't worry about using a welded 74 (or 78 for that matter) or a stock forged 71mm, as both are very strong and will work great in whatever combination you eventually choose to use.
Just remember not to go wild on the dispacement and stick to 96mm cast iron cylinders and you should be able to keep your engine more reliable, say vs using 103/105s. Otherwise, if you want more HP and to make it reliable, you'll want to invest some money in better cylinders, like Biral Babies or Nickies. We have tons of information on each product line on our web site at
http://www.LNengineering.com. I'd also recommend reading over Jake's website at
http://www.aircooledtechnology.com to see what combinations he has dreamed up and his comments on each of them.
Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance