The similarities between a Type 1 rocker assembly and one from a Type 4 are few. Like a Type 1, both are forged, and both rotate in a bushing manner. Whereas the Type 1 uses a single shaft for each head, the Type 4 uses one shaft per cylinder, making two rocker assemblies per head. The earlier models used 8mm adjusting screws, same as used on the Type 1, but the later models used a 10mm adjusting screw.
Engines originally equipped with solid cam/lifters had a spring between the two rocker arms on each assembly. The hydraulic cam engines used a solid spacer and is generally believed to be a better setup than the spring.
For mildly tuned engines, the stock rocker arms should be adequate. The one suggested ugrade would be to find a set of solid rocker spacers from a hydraulic lifter motor. This would eliminate the chance of the spring breaking between the intake and exhaust rocker arms. This can cause the rocker arms to wander on the shaft. This extra movement can cause a premature failure.
If you have your eye on driving this car hard, a set of early rocker arms with 8mm adjusting screws are advised. Substitute 911 style swivel feet adjusting screw and your rockers are ready to go. You will probably to spot face the camshaft to make up for the longer screw, but if done little at a time, you can get the rocker geometry right.
For hot street engines, the stock rocker assemblies with the early 8mm rocker arms. Combine these with 911 style adjusting screws, and chromoly rocker spacers from FAT Performance, and you'd have a dependable set of rockers.
For those that are looking for even more horsepower but aren't concerned about cost, Pauter Machine manufactures a set of 1.48 ratio roller tip rocker arms for the Type 4. These rockers require the use of a specially ground cam to effectively and safely, but your net horsepower will higher, if the heads are up to the challenge.
For out and out racing, no question: Pauter 1.48 roller tip rocker arms. These rockers will give you more lift than is safely possible with the stock 1.3. Just make to check that your valve springs and heads are up to the challenge. Check the retainer to valve guide clearance, and that your springs are strong enough to handle the rpm and rapid acceleration that this engine will put out. Use only the strongest chromoly pushrods, like a set of 160,000 psi pushrods from Gene Berg.