Yes, it will fit. I haven't needed to modify any trigger housings to fit my PF45's but if it needs a bit of sanding it won't take long.I didnt know the gen 5 trigger housing and arm was compatible with the PF45 frame, does that compadibility include the connector and ejector?
Have you found that the gen 5 housing also needs modification to fit properly?
You either need to modify your Gen 3 trigger arm or get a Gen 5 trigger arm and use a Gen 5 trigger housing. I've done both and the result is the same. Just cheaper to modify your trigger arm if you have parts laying around. The Gen 5 trigger assembly works the best of all assemblies and is a quantum leap for Glock trigger designs. Their designs are genius in their simplicity, but the Gen 5 assembly works fantastic.
You can also take the same housing and use it on all Glocks except 42, 43, and 48. Just takes a little modification to make it fit. Super easy and can be done very quickly with a Dremel or band sander. Of course, you will need the ejector for the round you are shooting but you only need to buy one housing for all your guns. It works so well that I have replaced pretty much all my Gen 3 and 4 housings with the Gen 5 standard and GPT on all those not running a Timney.