personally, I'd go with the 4" crank and 6.2-6.3" rods to minimize side loading if you want this to be something that's going to last 100k miles. the only heads out there with enough port volume and cross section for a 420+ inch small block are the big CNC indy's and the W7-8-9 IMHO.

for a street driver with the truck's weight and stall your cam choice doesn't sound too far off the mark, you're right, your .200" lift duration is probably more comparable to a flat tappet in the 230@.050 duration cam...I'd widen the LSA from 106. you'll sacrafice a bit of midrange torque, but flatten the torque curve out and extend it higher in the RPM range....something like a 112-114, installed on a 108ICL is what I'd do. should give you great power from near idle to 5500 RPM or so. I'd guess the narrow LSA cam you chose is going to nose over a little under 5k.