If you have any specific questions about how to build one or part numbers, just let me know...I suppose I am the resident expert on a build up of its kind.
Do you have to use different pistons? What is the closest aftermarket rod and from who? I am working on building a 351 and trying to use the most of the short block as I can.
Aftermarket pistons? Yes. With the longer rod the piston skirt becomes noticably shorter so as not to interfere with the long rod and the bore of the block. Both KB and JE make sets. The KB's can be had for under $350.00 and are awesome if you don't plan on running more than a 150 shot NOS or running massive boost. JE's are around $700.00 . . . enough said.
THe rods? Well as far as I know no one makes aftermarket rods that length. One could get custom rods but you don't need them. Grab yourself some rods out of either a 351M or a 400, have them shot peened and polished - they will hold a lot of HP. THey are heavy so dont plan on spinning more than 7200 RPMs with them.
The crank will remain the stock 351w, but the rods need a little more machining to get them to work. I had the Car SHop in Moline, Illinois (Davenport, IA area) do the work. They build "Uncle" Robin Lawerence's engines and many more Stang racers. Very knowledgable and affordable.
THe KB part number is KB - 333 and Summit carries them or the Car SHop can get them for a good price as well if you get the work done in house. I payed $0.00 for my rods - a friend payed $10.00 at a scrap yard. These are truck style rods so they never break, but it is a good idea to have them checked anyway.
I was thinking about a 6.2 inch Scat H-Beam rod and JE Inverted Dome Pisons for use with my standard stroke crank. The CR is just a hair under 10:1. I would prefer to use cheaper pistons but it appears that the only long rod the KB is set up for is the 400m, which is not available to me.