79 kz650 coil

hello I bought a #1 & 4 coil for my 79 kz650 on ebay and it is a little longer than the original coil on my bike. By longer I mean the actual black plastic coil housing is longer. The two bolts on the coil that attach to the frame are about 1/4" farther apart than the original. I realize that I will have to modify the bracket on the frame to install this coil but I am wondering if it will cause any other problems. I'm assuming it is for a later year 650?!?!

Any help would be much appreciated. Thanks!

The electrical characteristics are more important than size/mount issues which you will need to figure out. Measure the primary and secondary resistance and make sure both coils match. The coil primary and secondary resistance must match the ignition installed on your bike.

Check the numbers molded into the coil bodies. That will tell you something also. If the new coil has "TR" anywhere in the number molded into the plastic then that coil is for a bike that was originally equipped with electronic ignition.
As WG says, though, get out your multimeter and check both windings. Your 79 should/should have points ignition on it as stock so you need a coil with 4-5 ohms on the primary, IIRC.