Yes, different recommendations for different engines AND for different fuel systems. Fuel systems are speced and installed by the chassis maker.
Yes, the ISL does have an electric fuel pump, so cycling the key to on (not start position) does prime it.
I am a fan of prefilling the primary filter ONLY, then using the key to activate the fuel pump to fill the secondary.
Be aware that you will get different answers depending on level of fuel in the tank vs elevation of the primary fuel filter base. If level of fuel in the tank is lower (low on fuel and/or parked with nose down) when you remove the primary filter, fuel will RUN FROM FILTER BASE BACK TO THE TANK, LEAVING YOU WITH 25+' OF AIR IN THE LINE. Though it can be messy, better to have the level of fuel in the tank higher when changing filters. Yes, a little fuel will run out, but if you have the new filter ready to go, no big deal.
