There isn’t a straight swap with out altering for the ga range, it was very problematic anyway and got discontinued.
Best bet like kop says is to go for a new 600 series, it will definitely need pipework alteration, tbh there you’re kidding yourself if you’re looking for a straight easy swap these days, long gone are the days when you could chuck them on the wall in a morning and take your cash and run away. (Erm not that I ever did this BTW)
Boiler need a little care and attention, mag filters, water softeners, those little anti water hammer devices (I always forget what they’re called 🤪) boiler+ controls, setting up gas valves, cold flushing and hot flushing, and other bits I’ll remeber later.... paperwork, registering with gas safe, registering for warranty to give your customer piece of mind, little stickers on the front to remind them when the service is due.
All goes to making a good business model for yourself.
Good luck, let us know how you get on.