Legally - you cannot use that radio on the public service bands.
Let me explain - your amateur radio license only permits you to operate your part 97 radio on the amateur radio bands.

Although you can program or modify your radio to operate on the public service bands - either 150+ mhz or 450 mhz - but legally your radio is not approved to operate on those bands.

That is the reason why you cannot find any information - how to modify your radio to operate on those bands - because it is illegal.

I wish that more people would actually study the information on the tests for the amateur radio license and not just memorize the answers to pass the test and then call themselves ham radio operators.

One point to ponder - The FCC demanded that the local fire, police and ambulance change the way they broadcast their signals from a wide signal to a narrow signal. Most of the older police and fire Motorola radios did not have the capability to be changed to go from wide to narrow and so when it came time for our local counties to do so- they all migrated up into the 450 mhz bands.

For them it is illegal to use the wide bands.
Some counties are not in compliance and are still using the wide on the low band - such as 33 mhz for Indiana county PA

The reason why is because western Pennsylvania has very diverse terrain with tall mountains and deep valleys and the 450 mhz would require them to place a repeater about every 10 miles - which would be very cost prohibitive.
In comparison - running the low band - they have had forinstances where their ambulance was up in Erie PA - Hammot Medical center and they keyed up their mic and was able to talk back to Indiana county on their repeater - 120 miles away. You just can't do that with 450 mhz.

So until it all gets worked out - they will remain on the low band and each fireman has to either have a dual band radio to work different counties or they have to carry two seperate radios. The reason for that is - Jefferson county - Rossiter and Big Run is only seperated by about 5 miles and Punxsutawney is only about 6 road miles away. They all respond to each others calls. Without the mutual aid - it might take a fire company from Indiana county a hour to assemble and respond to a fire in the northern part of INdiana county because of the distance and the terrain between the other companies.