FYI - your mistakes are not rookie mistakes. The 3.5 is one of the most difficult motors to get together correctly that I've ever worked on - when I pulled the heads off of mine a number of years ago I had issues once I got it back together also. Turned out that I apparently didn't get some of the rocker arms securely in place - one of them had actually come off of the pivot and got stuck sideways under the cam, digging a groove in it's cam lobe. One of the others had come completely off. While I'm not an engine builder or mechanic by trade I've worked on numerous OHC engines over the years and consider myself to be pretty mechanically inclined - I've never had the kind of issues that I did with this engine.

Keep with it - we're keeping our fingers crossed for you!