I made my own as well, it really wasn't too bad just annoying having to be on my back so much to take measurements and keep re-checking the fit. Buddy of mine works at a metal supply yard so I got two ~60" sections of 1/8" wall thickness 2x3" mild steel box tubing for $40 and just cut them up. Same friend also has a pretty good MIG welder so one Saturday I went over to his place and booger'd them in.
One thing's for sure, whatever the initial rust-prevention primer/coating they put on the unibody from the factory is strong as HELL, I couldn't get it all off with a wire wheel and I ended up having a hard time with the welding it really didn't want to arc to the body easily (and that's where my ground was attached). Media blasting or carefully burning it off would probably help. Also the fact that the rear frame rails are tapered made it a challenge to keep the gaps small enough. Welding the front sides to the trans crossmember was a piece of cake though.