Battery fit question

[85 DSEL]

When I acquired my 'spare' w123 300DT car a few years ago it had what appeared to be a fairly new battery in it. So, I removed it, took it to my garage and there it has remained on a shelf. I have on occasion hooked up a trickle charger to it just to keep a charge on it. It will need to be determined if it is a 'good' unit before attempting to use it as a primary power source.

My w124 gasser (1995 E320 wagon) is going to need the battery replaced (as revealed to me by the MB dealership that performed my pre-purchase inspection back in August). The physical size of its battery is somewhat smaller than the 'spare' one. The battery tray appears large enough to accommodate the larger size - considering that many of these cars were manufactured with diesel power which would require the larger size. Now to the 'nut' of this post:

Is there any reason why this battery would not perform well in the car , in spite of its larger size? Just looking at options available to me. Thanks guys, you're the best