I've been wanting to build a model for my father to depict his HMMWV that he had in 1991. I've been waiting for him to dig out his old photo album so I could see pictures of it. It looks like it may not be as straight forward as I ha hoped. I want to build this as accurate as possible, for him. By looking at the picture, it looks like I'll be doing a fair bit of scratch building. Which I have never done.
Here is the picture.

By looking at this picture, and talking to him, he said they placed wood 4x4s on top strapped down. They also built a plywood box in the back to store their gear. So I guess my first question is, where is the best place to buy scale plywood and 4x4s?
Also looks like I'll be needing something to represent angle iron.
I was also thinking about using this to represent weight.

Will it work with the Tamiya M1025?
His HMMWV doesn't look weighted down like some from the 2003ish era, but definitely doesn't seem to be riding as high as the ones I worked on with no weight in them.
I was also going to pick up a set of DEF model sagged wheels R/T II.
Can anyone recommend a PE set that would help set this off?
I know these are a lot of questions. This is a surprise for him, and I really want it to be just like the picture.
Thanks for any help,
Dustin
EDIT: I'll also be using the MIG conversion 35-121 kit.