1992 Mercruiser 4.3 block discontinued

Hello all, I have a question and I'm hoping to get some guidance. I just picked up a second boat as a project. The mercruiser 4.3 starts but knocks and bangs pretty bad. It's from 1992 and I think I want to drop in a remanufactured long block instead of trying to rebuild it. When I look up the long block model 14149A1 it says no longer available. My question is what do I use as a replacement block and what has to be done to make it work? I don't have much experience going this deep in to an engine but I am eager to learn. Pulling the out drive and engine looks pretty straightforward and transferring all of the accessories and such doesn't seem to be a big deal either. I just get lost dealing with the different models of this engine. Any info would be greatly appreciated. I can also get more details on the existing engine if needed. Thank You

Ayuh,..... Update to a '96 or newer to get the vortec heads,..... those heads are worth 20/ 25 hp,....

You'll need a newer intake manifold, 'n have to add an electric fuel pump,.....

Yer other bits, 'n pieces will bolt right on,.....

Great, thanks for the info. Any idea if I would have to change the motor mounts since it's not a balanced engine?