I've done the TFI or juice box upgrade on several cj/yj 258s (see the write up
here), and I think the main reason that you would want to use a larger cap and rotor (on the 25
is that the cap the factory used was too small, and caused problems. Your Cherokee probably doesn't have this problem as it uses a different distributor.
The juice box gets most of it's power from the new plug wires and coil. I would recommend that before you spend the time trying to discover new parts that fit, you get a new set of wires and a coil from someone like Accel or MSD.
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Terry Mason:
'85 CJ-7 - 33s, total of 4.5" lift,
TFI ignition, plus more.
Click here to see it