What year is your Bronco?
The factory tray had seen a better day in my '85 like most first gens (similar to 84-88 Bronco II's)
So I removed it, drilled three holes
And installed a bricknose (87-90ish) fullsize tray
And now it takes a 65 class battery
The MTP-65HD I have is 850CCA and 1000CA.
BUT watch out around the tray. I think a 2.8 would be ok (watch alternator) and I think a first gen 2.9 would be similar aside from possible airbox interferance. A 89-90 has a different tray that is riveted in and sits at an angle and it may not fit at all with one of those.
Just an idea for a possible upgrade, especially if you have a first gen and your tray is toast like most. Really a quality replacement battery should be enough.