I got this from a book called How to build BIG inch Mopar small blocks. I know Barnes and Nobles has it.
A 4.04in bore with a 4.25 crank will get you 435 ci. if you want as close to 426 as you can get, you need a 4.2 crank and a 4.02 bore, or a 4.15 in crank and a 4.045 in bore. A 4.1 in stroke (Seems to be the norm) and a 4.05 in bore is only 422 ci. A good cam for the street is Mopar 4876348. .501 in lift w/ 230/234 Duration. Good for about 10 sec's. Use the early 360 as it has more meat where you need it. The '75 up to the Magnums are all thin wall castings and not a good choice. Magnum's are a good choice. I'm still looking for the cylinder mod's, rod's and pistons. Bore x bore x stroke x # cyl's x .785 = C I's. for heads, use Mopar # P5007141. has 2.02" valves. W/ a good valve job you can stuff 2.08" nail head valves in them. Does this help?