I know a bit on this because I was planning to build a stroker myself before i picked up a 350 and 700r4 for dirt cheap running great with 80,000 miles on it. (Being nice to neighbors pays off
) So A 4.0 is basically the same block as the 4.2 but heres the difference. The crankshaft, rods and bore of the pistons. The 4.0 has a smaller stroke then the 4.2 but a bigger bore. So to get to the 4.6 or 4.7 get yourself a 4.2 crankshaft and rods. It should go into the 4.0 with little to no machining. Next it probably would be a good idea to put in some new pistons since you have it apart (this includes rings) So why not bore it out a bit more for more power and more displacment. You can safely bore it over 0.03 but id go with 0.02 to be safe. And you can also play with the compression ratio if your up to it to try to squeeze out more power.