Replacement alternator loose on bracket

[whaleshark]

Couldn't find anyone else with this same problem on internet which is unusual - perhaps I am uniquely stupid this time.

I had the 'alternator workshop' so took old alternator out and took it to ECP and TPS, but the 'matching' units that they sell have slightly different width brackets - ie the 'arms' on the alternator - including the threaded insert are about 6mm too wide. So if I were to insert the bolts from the front, through the fixed bracket into the rear threaded insert in the alternator 'arm' the alternator would have a lot of slop and slide around forward and back around 6mm.

I didn't pick up the replacements alternators but there is one possibility that has occurred to me. If I were to do as above and tighten the bolts would the threaded inserts in the arms of the alternator pull through and so tighten up?

Hope that makes some sense!