Great result with the engine change! VW 504.00/VW 507.00 oils are low SAPS- they have low levels of additives, means oil which is burned/ returned to the intake via PCV has less solids which will stick to the intake valves. I use this Roadmaster VW | Anglomoil as I get it by the 20L drum for a good price. These oils are group 5 synthetics (ester) and use the most expensive base stocks.

VW502.00/VW505.00 oils can also be used- you can get these in the heavier 5w40 weight. They have more additives- zinc for antiwear, Calcuim as a detergent, etc. and are usually a cheaper base stock- group 3 and 4 synthetics. I would recommend these oils if I was racing/ driving hard and change it at half the interval (7500ks on the road, or more often if tracking the car).

Make sure you break in the new engine well. Make sure the rings seat properly. Here's the guide Break In Secrets--How To Break In New Motorcycle and Car Engines For More Power