Thanks.
The whole rear frame as you see it is going to be the air tank. I cut holes in the rails to let air into the mid crossmember, where the valves will mount. I was pressure testing it in that picture, trying to find leaks. I found none with the soapy water technique, and it held 120 PSI for over an hour. But I am leaving it overnight to see how well it holds.
I put some blind tapped bungs in the bottom of the rail to mount a low profile bump stop.
Is it okay to continue this kind of project thread here?