Gordy, with most of these threads that I follow, including my own, I always learn way more than I ever contribute!! Thus, I look forward to responses regarding suspension, etc. since some of what I learn here may affect how I continue with my own project.

I'm certainly no frame or suspension guru of any kind but since you have boxed your frame and added that beefy x-member, I would think you've removed the lion's share of the twisting & flexing, compared to how Henry originally made it. Plus, I highly doubt you'll ever be hauling a 1/2 ton of gravel or a thousand pounds of plywood in it. I say all that because some of your concerns about suspension travel & frame flexing may never be an issue for this truck given how you're probably going to drive it. Just a thought...

As always, looking forward to the next wave of comments & progress.