i just used 10 Gage plate from work.
you get stronger steel with the MII for the front.
we have a plasma table so i just gave the programmer the dimensions and he blasted it off for me.
The frame is quite even from the end of the boxing plate to the rise of the rear diff.
I just put some weld through primer inside to help prevent rust etc.
The truck probably wont see any rain/elements anyway so I'm not to worried about inner frame rust.
Just make sure you have good penetration and you should be good.
They made these old truck out of decent steel so i think 10 gage is fine.
What way are you going to go with your truck?
stock front? MII?
Here is one i followed to install mine:
http://www.classictrucks.com/tech/0903clt_1939_chevy_truck_total_cost_involved_ifs_upgrade/hope this helps.
Barry
