Your RB 5 port has similar porting and cuts as the Richey engines but the crank timing on the Richey is different.
You can compare it with the stock MT12. At first, I had no idea how the Richey mods looked like or why it was so much more powerful. I looked at LittoDeviL's mods (his mods were based on seeing the Richey pics but his engine mods turned out to be a fiasco) and I still didn't understand how it worked because of his poor craftsmanship and little effort.
But after opening up an RTU and comparing it to a stock MT12, I got an idea of why certain cuts were made drawing in a faster fuel/air mixture to the combustion chamber where claw marks were used as a guide for the transfer ports (which also has been modified.) The crank is also a work of art forming a scoop for the mixture and enlarged intake. Bored and polished carb, modified and lowered head button for higher compression ratio, and skirted piston. But of course, to get to the point of becoming like Dennis, it will take years and many engines...
After seeing RTO's and RTU's run, the Richey engines are worth every penny.
I'll stick with my stock MT12 and CVR, they are already plenty for me.