79-86 guys, I need a battery tray!

[red82gt]

The skinny stock battery in my car doesn't crank out enough power to start my car. I had an 87up battery (died, replaced on warranty with the correct '82 size battery)in my car and had it strapped down with a bungee cord and of course this won't get by a tech inspector. I tried to fit an 87 up mustang tray in my car but it will not fit. What should I do? Right now I don't have the funds to relocate it to the hatch (NHRA legal box) so what should I do? Should I make my own tray out of something? I just want something that'll hold a bigger battery and it will be secure, any suggestions?

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GT-40 heads (ported, polished, + milled), B303 cam, 1.7rr's, JE pistons, Offy intake, Carter AFB 625cfm carb, Flowtech 1 5/8" shortys, Flowtech X-pipe, MAC Flowpath exhaust, MAC pulleys, 373's, subframes, Eibachs+Tokicos, B&M ripper, FMS Clutch, Zoom Quadrant+cable, 17" CSA Ultra rims, 235/45ZR17 Yokohama AVS S4's, MSD 6A ignition+coil, FMS 9mm wires, Carbed, Naturally Aspirated, and Nasty!