so I've been following this thread with a ton of interest and I've come to the conclusion that the stock rockers are about the best option for the slant six nation please correct me if I'm wrong
Here is a photo of a slant 6 rocker arm with a piece of spaghetti showing a straight path that could be cut to enable the adjuster screw to be moved about .080" toward the shaft, which would increase the lift ratio somewhat. I did some measuring and that amount seemed to be about right for a 1.6:1 geometry.
Those rockers are heat treated, so it's going to take an aggressive cutter to get the job done. Once they are in 2 pieces, a jig will have to be used to hold them in proper alignment for proper welding.
Someone (probably Aaron???) might have the skills to accomplish this. I would try it, but I KNOW there are guys out there who could do this blindfolded, while ~I~ was thinking about it...