The trick is to use the Chevy rods. They are made in much higher volume so you can get higher quality rods for less money. For a 512 you should be able to use a very common 6.535 rod. Another great benefit of using the Chevy rod is that then you can use Chevy rod bearings. There are a ton of those bearings available including different widths, coatings, etc.

If it was me I'd probably go with the Molnar crank, some SCAT H beam rods and the SRP pistons. That combo should fall together and make really nice power with the TF heads.