With a little help from Wil, I believe I've corrected this issue.
Wil suggested I check the valve clearance and timing. Timing marks all seemed to line up. However, valves were nearly all overtightened. Brought ever valve back to within spec (.004 intake, .007 exhaust) and just finished reassembling. I'm going to give the RTV a few hours to set up, then go out and crank her up. Fingers crossed, knock on wood, I hope I solved this issue.
Wil suggested I check the valve clearance and timing. Timing marks all seemed to line up. However, valves were nearly all overtightened. Brought ever valve back to within spec (.004 intake, .007 exhaust) and just finished reassembling. I'm going to give the RTV a few hours to set up, then go out and crank her up. Fingers crossed, knock on wood, I hope I solved this issue.